[kuangbin]带你飞之'网络流'专题
专题十一 网络流
√ POJ 3281 Dining
√ POJ 1087 A Plug for UNIX
√ POJ 2195 Going Home
√ POJ 2516 Minimum Cost
√ POJ 1459 Power Network
√ HDU 4280 Island Transport
√ HDU 4292 Food
√ HDU 4289 Control
√ UVA 10480 Sabotage
√ HDU 2732 Leapin' Lizards
√ HDU 3338 Kakuro Extension
√ HDU 3605 Escape
√ HDU 3081 Marriage Match II
√ HDU 3416 Marriage Match IV
// poj 3281 最大流 水
1 #include<cstdio> 2 #include<algorithm> 3 #include<queue> 4 #define INF 0x3f3f3f3f 5 using namespace std; 6 7 inline int read() { 8 char c=getchar();int x=0,f=1; 9 while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();} 10 while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();} 11 return x*f; 12 } 13 14 const int MAXN = 30000+5; 15 const int MAXE = 20400+5; 16 17 int num; 18 int head[MAXN]; 19 struct node { 20 int v, flow; 21 int next; 22 } edge[MAXE]; 23 24 inline void add(int x, int y, int w) { 25 edge[num].v = y; 26 edge[num].flow = w; 27 edge[num].next = head[x]; 28 head[x] = num++; 29 } 30 31 int n, cows, food, drink; 32 int cur[MAXN], dis[MAXN]; 33 34 bool bfs() { 35 for(int i = 1; i <= n; ++i) dis[i] = 0; 36 dis[1] = 1; 37 queue<int> q; 38 q.push(1); 39 while(!q.empty()) { 40 int u = q.front(); 41 q.pop(); 42 for(int i = head[u]; i != -1; i = edge[i].next) { 43 int v = edge[i].v; 44 if(!dis[v] && edge[i].flow) { 45 dis[v] = dis[u] + 1; 46 q.push(v); 47 } 48 } 49 } 50 return dis[n] != 0; 51 } 52 53 int dfs(int u, int f) { 54 if(u == n || (!f)) return f; 55 int flow = 0; 56 for(int& i = cur[u]; i != -1; i = edge[i].next) { 57 int v = edge[i].v; 58 if(dis[v] == dis[u] + 1) { 59 int di = dfs(v, min(f, edge[i].flow)); 60 if(di > 0) { 61 flow += di; 62 f -= di; 63 edge[i].flow -= di; 64 edge[i^1].flow += di; 65 if(!f) break; 66 } 67 } 68 } 69 if(!flow) dis[u] = -1; 70 return flow; 71 } 72 73 int Dinic() { 74 int ans = 0; 75 while(bfs()) { 76 for(int i = 1; i <= n; ++i) cur[i] = head[i]; 77 ans += dfs(1, INF); 78 } 79 return ans; 80 } 81 82 83 int main() { 84 cows = read(); food = read(); drink = read(); 85 n = cows*2 + food + drink + 2; 86 num = 0; 87 for(int i = 1; i <= n; ++i) head[i] = -1; 88 for(int i = 2; i <= 1+food; ++i) { 89 add(1, i, 1); 90 add(i, 1, 0); 91 } 92 for(int i = 2+food+cows*2; i <= 1+food+cows*2+drink; ++i) { 93 add(i, n, 1); 94 add(n, i, 0); 95 } 96 int fn, dn, x; 97 for(int i = 2+food; i <= 1+food+cows; ++i) { 98 fn = read(); dn = read(); 99 for(int j = 0; j != fn; ++j) { 100 x = read(); 101 add(1+x, i, 1); 102 add(i, 1+x, 0); 103 } 104 for(int j = 0; j != dn; ++j) { 105 x = read(); 106 add(i+cows, 1+food+cows*2+x, 1); 107 add(1+food+cows*2+x, i+cows, 0); 108 } 109 add(i, i+cows, 1); 110 add(i+cows, i, 0); 111 } 112 printf("%d\n", Dinic()); 113 return 0; 114 }
// poj 1087 最大流 + flody
1 #include<cstdio> 2 #include<iostream> 3 #include<algorithm> 4 #include<string> 5 #include<queue> 6 #include<map> 7 #include<set> 8 #define INF 0x3f3f3f3f 9 using namespace std; 10 const int MAXN = 10000+5; 11 const int MAXE = 80000+5; 12 typedef pair<string, string> Pair; 13 14 int num; 15 int head[MAXN]; 16 struct node { 17 int v, w; 18 int next; 19 } edge[MAXE]; 20 21 inline void add(int x, int y, int w) { 22 edge[num].v = y; 23 edge[num].w = w; 24 edge[num].next = head[x]; 25 head[x] = num++; 26 } 27 28 int cz, things, type, n; 29 string name; 30 map<int, string> id; 31 string a, b; 32 vector<Pair> wp; 33 vector<Pair> tp; 34 int G[MAXN][MAXN]; 35 36 int cur[MAXN]; 37 int dis[MAXN]; 38 39 bool bfs() { 40 for(int i = 1; i <= n; ++i) dis[i] = 0; 41 dis[1] = 1; 42 queue<int> q; 43 q.push(1); 44 while(!q.empty()) { 45 int u = q.front(); 46 q.pop(); 47 for(int i = head[u]; i != -1; i = edge[i].next) { 48 int v = edge[i].v; 49 if(!dis[v] && edge[i].w) { 50 dis[v] = dis[u] + 1; 51 q.push(v); 52 } 53 } 54 } 55 return dis[n] != 0; 56 } 57 58 int dfs(int u, int f) { 59 if(u == n || (!f)) return f; 60 int flow = 0; 61 for(int& i = cur[u]; i != -1; i = edge[i].next) { 62 int v = edge[i].v; 63 if(dis[v] == dis[u] + 1) { 64 int di = dfs(v, min(f, edge[i].w)); 65 if(di) { 66 flow += di; 67 f -= di; 68 edge[i].w -= di; 69 edge[i^1].w += di; 70 if(!f) break; 71 } 72 } 73 } 74 if(!f) dis[u] = -1; 75 return flow; 76 } 77 78 int Dinic() { 79 int ans = 0; 80 while(bfs()) { 81 for(int i = 1; i <= n; ++i) cur[i] = head[i]; 82 ans += dfs(1, INF); 83 } 84 return things - ans; 85 } 86 87 void flody() { 88 map<int, string> tt; 89 map<string, int> id2; 90 int cnt = 0; 91 for(int i = 0; i != type; ++i) { 92 cin >> b >> a; 93 if(!id2.count(a)) tt[++cnt] = a, id2[a] = cnt; 94 if(!id2.count(b)) tt[++cnt] = b, id2[b] = cnt; 95 G[id2[a]][id2[b]] = 1; 96 } 97 for(int k = 1; k <= cnt; ++k) { 98 for(int i = 1; i <= cnt; ++i) { 99 if(!G[i][k]) continue; 100 for(int j = 1; j <= cnt; ++j) { 101 if(G[k][j]) G[i][j] = 1; 102 } 103 } 104 } 105 type = 0; 106 for(int i = 1; i <= cnt; ++i) { 107 for(int j = 1; j <= cnt; ++j) { 108 if(G[i][j]) { 109 tp.push_back(make_pair(tt[i], tt[j])); 110 ++type; 111 } 112 } 113 } 114 //printf("----%d\n", type); 115 } 116 117 int main() { 118 scanf("%d", &cz); 119 for(int i = 2; i <= 1+cz; ++i) { 120 cin >> name; 121 id[i] = name; 122 } 123 scanf("%d", &things); 124 for(int i = 0; i != things; ++i) { 125 cin >> a >> b; 126 wp.push_back(make_pair(a, b)); 127 } 128 scanf("%d", &type); 129 flody(); 130 n = cz + things + type + 2; 131 num = 0; 132 for(int i = 1; i <= n; ++i) head[i] = -1; 133 for(int i = 2; i <= 1+cz; ++i) { 134 add(1, i, 1); 135 add(i, 1, 0); 136 } 137 for(int i = 2+cz+type; i <= 1+cz+type+things; ++i) { 138 add(i, n, 1); 139 add(n, i, 0); 140 } 141 for(int i = 0; i != wp.size(); ++i) { 142 for(int j = 2; j <= 1+cz; ++j) { 143 if(id[j] == wp[i].second) { 144 add(j, 2+cz+type+i, 1); 145 add(2+cz+type+i, j, 0); 146 break; 147 } 148 } 149 } 150 for(int i = 0; i != tp.size(); ++i) { 151 a = tp[i].first; b = tp[i].second; 152 for(int j = 2; j <= 1+cz; ++j) { 153 if(id[j] == a) { 154 add(j, 2+cz+i, 1); 155 add(2+cz+i, j, 0); 156 break; 157 } 158 } 159 for(int j = 0; j != wp.size(); ++j) { 160 if(b == wp[j].second) { 161 add(2+cz+i, 2+cz+type+j, 1); 162 add(2+cz+type+j, 2+cz+i, 0); 163 } 164 } 165 } 166 printf("%d\n", Dinic()); 167 return 0; 168 }
// poj 2195//KM写的。
1 #include<cstdio> 2 #include<cstring> 3 #include<cmath> 4 #include<fstream> 5 #include<iostream> 6 #include<string> 7 #include<functional> 8 #include<algorithm> 9 #include<sstream> 10 #include<iomanip> 11 #include<vector> 12 #include<queue> 13 #include<stack> 14 #include<set> 15 #include<map> 16 #define read(n) n = read_n() 17 #define rep(i, n) for(int i=0;i!=n;++i) 18 #define per(i, n) for(int i=n-1;i>=0;--i) 19 #define Rep(i, sta, n) for(int i=sta;i!=n;++i) 20 #define rep1(i, n) for(int i=1;i<=n;++i) 21 #define per1(i, n) for(int i=n;i>=1;--i) 22 #define Rep1(i, sta, n) for(int i=sta;i<=n;++i) 23 #define L k<<1 24 #define R k<<1|1 25 #define mid (tree[k].l+tree[k].r)>>1 26 #define eps 1e-10 27 using namespace std; 28 typedef long long ll; 29 typedef pair<int,int> Pair; 30 const int INF = 0x3f3f3f3f; 31 32 inline int read_n() { 33 char c=getchar();int x=0,f=1; 34 while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();} 35 while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();} 36 return x*f; 37 } 38 inline void put(int a) { 39 if(a<0){putchar('-');a=-a;} 40 if(a>9)put(a/10); 41 putchar(a%10+'0'); 42 } 43 // ----------------------------------------------------- 44 const int MAXN = 100+5; 45 46 int r, c; 47 int n, m; 48 int w[MAXN][MAXN]; 49 50 int love[MAXN]; 51 bool visx[MAXN], visy[MAXN]; 52 int cx[MAXN], cy[MAXN]; 53 54 bool dfs(int u) { 55 visx[u] = true; 56 for(int v = 1; v <= m; ++v) { 57 if(!visy[v] && cx[u] + cy[v] == w[u][v]) { 58 visy[v] = true; 59 if(!love[v] || dfs(love[v])) { 60 love[v] = u; 61 return true; 62 } 63 } 64 } 65 return false; 66 } 67 68 int KM() { 69 rep1(i, m) love[i] = 0; 70 rep1(i, n) { 71 while(1) { 72 int d = INF; 73 rep1(j, n) visx[j] = visy[j] = false; 74 if(dfs(i)) break; 75 for(int u = 1; u <= n; ++u) { 76 if(visx[u]) { 77 for(int v = 1; v <= m; ++v) { 78 if(!visy[v]) { 79 d = min(d, cx[u] + cy[v] - w[u][v]); 80 } 81 } 82 } 83 } 84 rep1(u, n) if(visx[u]) cx[u] -= d; 85 rep1(v, m) if(visy[v]) cy[v] += d; 86 } 87 } 88 int ans = 0; 89 rep1(i, m) ans += w[love[i]][i]; 90 return -ans; 91 } 92 93 int main() { 94 while(scanf("%d%d", &r, &c) == 2 && r) { 95 n = m = 0; 96 rep1(i, 100) love[i] = cy[i] = 0, cx[i] = -INF; 97 char p[MAXN]; 98 vector<Pair> man, house; 99 rep(i, r) { 100 scanf("%s", p); 101 rep(j, c) { 102 if(p[j] == 'm') ++n, man.push_back(make_pair(i, j)); 103 if(p[j] == 'H') ++m, house.push_back(make_pair(i, j)); 104 } 105 } 106 rep(i, man.size()) { 107 rep(j, house.size()) { 108 w[i+1][j+1] = -abs(man[i].first - house[j].first) - abs(man[i].second - house[j].second); 109 cx[i+1] = max(cx[i+1], w[i+1][j+1]); 110 } 111 } 112 printf("%d\n", KM()); 113 } 114 return 0; 115 }
// poj 2516 最小费用最大流 拆图
1 /* 2 * @Promlem: 3 * @Time Limit: ms 4 * @Memory Limit: k 5 * @Author: pupil-XJ 6 * @Date: 2019-11-11 22:37:28 7 * @LastEditTime: 2019-11-12 11:13:39 8 */ 9 #include<cstdio> 10 #include<ctime> 11 #include<algorithm> 12 #include<stack> 13 #include<map> 14 using namespace std; 15 const int INF = 0x3f3f3f3f; 16 typedef pair<int,int> Pair; 17 const int MAXN = 800+5; 18 const int MAXE = 102000+5; 19 20 int num; 21 int head[MAXN]; 22 struct node { 23 int v, flow, dis; 24 int next; 25 } edge[MAXE]; 26 27 inline void add(int x, int y, int w, int d) { 28 edge[num].v = y; 29 edge[num].flow = w; 30 edge[num].dis = d; 31 edge[num].next = head[x]; 32 head[x] = num++; 33 } 34 35 int n, m, k, sum; 36 int S, T; 37 38 int maxflow, mincost; 39 int flow[MAXN], dis[MAXN]; 40 int pre[MAXN], last[MAXN]; 41 bool vis[MAXN]; 42 43 bool spfa() { 44 for(int i = 1; i <= T; ++i) flow[i] = dis[i] = INF, vis[i] = false; 45 dis[S] = 0; 46 vis[S] = true; 47 pre[T] = -1; 48 stack<int> q; 49 q.push(S); 50 while(!q.empty()) { 51 int u = q.top(); 52 q.pop(); 53 vis[u] = false; 54 for(int i = head[u]; i != -1; i = edge[i].next) { 55 int v = edge[i].v; 56 if(edge[i].flow && dis[v] > dis[u] + edge[i].dis) { 57 dis[v] = dis[u] + edge[i].dis; 58 pre[v] = u; 59 last[v] = i; 60 flow[v] = min(flow[u], edge[i].flow); 61 if(!vis[v]) { 62 vis[v] = true; 63 q.push(v); 64 } 65 } 66 } 67 } 68 return pre[T] != -1; 69 } 70 71 bool MCMF() { 72 maxflow = mincost = 0; 73 while(spfa()) { 74 maxflow += flow[T]; 75 mincost += flow[T]*dis[T]; 76 int u = T; 77 while(u != S) { 78 edge[last[u]].flow -= flow[T]; 79 edge[last[u]^1].flow += flow[T]; 80 u = pre[u]; 81 } 82 } 83 return maxflow == sum; 84 } 85 86 int need[155][155], have[155][155], cost[155][155][155]; 87 88 void draw(int k_num) { 89 S = 1; T = 2+m+n; 90 num = sum = 0; 91 for(int i = 1; i <= T; ++i) head[i] = -1; 92 for(int i = 2; i <= 1+m; ++i) { 93 add(S, i, have[i-1][k_num], 0); 94 add(i, S, 0, 0); 95 } 96 for(int i = 2; i <= 1+m; ++i) { 97 for(int j = 2+m; j <= 1+m+n; ++j) { 98 add(i, j, INF, cost[j-1-m][i-1][k_num]); 99 add(j, i, 0, -cost[j-1-m][i-1][k_num]); 100 } 101 } 102 for(int i = 2+m; i <= 1+m+n; ++i) { 103 add(i, T, need[i-1-m][k_num], 0); 104 add(T, i, 0, 0); 105 sum += need[i-1-m][k_num]; 106 } 107 } 108 109 int solve() { 110 int ans = 0; 111 for(int i = 1; i <= k; ++i) { 112 draw(i); 113 if(MCMF()) ans += mincost; 114 else return -1; 115 } 116 return ans; 117 } 118 119 void input() { 120 int x; 121 for(int i = 1; i <= n; ++i) { 122 for(int j = 1; j <= k; ++j) { 123 scanf("%d", &x); 124 need[i][j] = x; 125 } 126 } 127 for(int i = 1; i <= m; ++i) { 128 for(int j = 1; j <= k; ++j) { 129 scanf("%d", &x); 130 have[i][j] = x; 131 } 132 } 133 for(int i = 1; i <= k; ++i) { 134 for(int u = 1; u <= n; ++u) { 135 for(int v = 1; v <= m; ++v) { 136 scanf("%d", &x); 137 cost[u][v][i] = x; 138 } 139 } 140 } 141 } 142 143 int main() { 144 while(1) { 145 scanf("%d%d%d", &n, &m, &k); 146 if(!n) break; 147 input(); 148 printf("%d\n", solve()); 149 } 150 return 0; 151 }
// poj 1459 最大流 水
1 #include<cstdio> 2 #include<algorithm> 3 #include<queue> 4 #define INF 0x3f3f3f3f 5 using namespace std; 6 const int MAXN = 102+5; 7 const int MAXE = 40200+5; 8 9 int num; 10 int head[MAXN]; 11 struct node { 12 int v, flow; 13 int next; 14 } edge[MAXE]; 15 16 inline void add(int x, int y, int w) { 17 edge[num].v = y; 18 edge[num].flow = w; 19 edge[num].next = head[x]; 20 head[x] = num++; 21 } 22 23 int n, np, nc, m; 24 25 int dis[MAXN], cur[MAXN]; 26 bool vis[MAXN]; 27 28 bool bfs() { 29 for(int i = 1; i <= n; ++i) dis[i] = 0; 30 dis[1] = 1; 31 queue<int> q; 32 q.push(1); 33 while(!q.empty()) { 34 int u = q.front(); 35 q.pop(); 36 for(int i = head[u]; i != -1; i = edge[i].next) { 37 int v = edge[i].v; 38 if(!dis[v] && edge[i].flow) { 39 dis[v] = dis[u] + 1; 40 q.push(v); 41 } 42 } 43 } 44 return dis[n] != 0; 45 } 46 47 int dfs(int u, int f) { 48 if(u == n || (!f)) return f; 49 int flow = 0; 50 for(int& i = cur[u]; i != -1; i = edge[i].next) { 51 int v = edge[i].v; 52 if(dis[v] == dis[u] + 1) { 53 int di = dfs(v, min(f, edge[i].flow)); 54 if(di > 0) { 55 f -= di; 56 flow += di; 57 edge[i].flow -= di; 58 edge[i^1].flow += di; 59 if(!f) break; 60 } 61 } 62 } 63 if(!flow) dis[u] = -1; 64 return flow; 65 } 66 67 int Dinic() { 68 int ans = 0; 69 while(bfs()) { 70 for(int i = 1; i <= n; ++i) cur[i] = head[i]; 71 ans += dfs(1, INF); 72 } 73 return ans; 74 } 75 76 int main() { 77 while(scanf("%d%d%d%d", &n, &np, &nc, &m) == 4) { 78 n = n+2; 79 num = 0; 80 for(int i = 1; i <= n; ++i) head[i] = -1; 81 char c; 82 int x, y, w; 83 for(int i = 0; i != m; ++i) { 84 c = getchar(); 85 while(c != '(') c = getchar(); 86 scanf("%d,%d)%d", &x, &y, &w); 87 add(x+2, y+2, w); 88 add(y+2, x+2, 0); 89 } 90 for(int i = 0; i != np; ++i) { 91 c = getchar(); 92 while(c != '(') c = getchar(); 93 scanf("%d)%d", &x, &w); 94 add(1, x+2, w); 95 add(x+2, 1, 0); 96 } 97 for(int i = 0; i != nc; ++i) { 98 c = getchar(); 99 while(c != '(') c = getchar(); 100 scanf("%d)%d", &x, &w); 101 add(x+2, n, w); 102 add(n, x+2, 0); 103 } 104 printf("%d\n", Dinic()); 105 } 106 return 0; 107 }
// hdu 4280 最大流水(无向图 反向边权值和正向边权值相等)
1 #include<cstdio> 2 #include<algorithm> 3 #include<queue> 4 #define INF 0x3f3f3f3f 5 using namespace std; 6 7 inline int read() { 8 char c=getchar();int x=0,f=1; 9 while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();} 10 while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();} 11 return x*f; 12 } 13 14 const int MAXN = 100002+5; 15 const int MAXE = 200002+5; 16 17 int num; 18 int head[MAXN]; 19 struct node { 20 int v, flow; 21 int next; 22 } edge[MAXE]; 23 24 inline void add(int x, int y, int w) { 25 edge[num].v = y; 26 edge[num].flow = w; 27 edge[num].next = head[x]; 28 head[x] = num++; 29 } 30 31 int n, m; 32 int S, T; 33 int dis[MAXN], cur[MAXN]; 34 35 int q[MAXN]; 36 bool bfs() { 37 for(int i = 1; i <= n; ++i) dis[i] = 0; 38 dis[S] = 1; 39 int l = 1, r = 1; 40 q[1] = S; 41 while(l <= r) { 42 int u = q[l]; 43 if(u == T) return true; 44 ++l; 45 for(int i = head[u]; i != -1; i = edge[i].next) { 46 int v = edge[i].v; 47 if(!dis[v] && edge[i].flow) { 48 dis[v] = dis[u] + 1; 49 q[++r] = v; 50 } 51 } 52 } 53 return dis[T] != 0; 54 } 55 56 int dfs(int u, int f) { 57 if(u == T || (!f)) return f; 58 int flow = 0; 59 for(int& i = cur[u]; i != -1; i = edge[i].next) { 60 int v = edge[i].v; 61 if(dis[v] == dis[u] + 1) { 62 int di = dfs(v, min(f, edge[i].flow)); 63 if(di > 0) { 64 f -= di; 65 flow += di; 66 edge[i].flow -= di; 67 edge[i^1].flow += di; 68 if(!f) break; 69 } 70 } 71 } 72 if(!flow) dis[u] = -1; 73 return flow; 74 } 75 76 int Dinic() { 77 int ans = 0; 78 while(bfs()) { 79 for(int i = 1; i <= n; ++i) cur[i] = head[i]; 80 ans += dfs(S, INF); 81 } 82 return ans; 83 } 84 85 int main() { 86 int qaq = read(); 87 while(qaq--) { 88 n = read(); m = read(); 89 int l = INF, r = -INF; 90 int x, y, w; 91 for(int i = 1; i <= n; ++i) { 92 x = read(); y = read(); 93 if(x < l) S = i, l = x; 94 if(x > r) T = i, r = x; 95 head[i] = -1; 96 } 97 num = 0; 98 for(int i = 0; i != m; ++i) { 99 x = read(); y = read(); w = read(); 100 add(x, y, w); 101 add(y, x, w); 102 } 103 printf("%d\n", Dinic()); 104 } 105 return 0; 106 }
// hdu 4292 最大流 拆点 水
1 #include<cstdio> 2 #include<algorithm> 3 #include<queue> 4 #pragma comment(linker, "/STACK:102400000,102400000") 5 #define INF 0x3f3f3f3f 6 using namespace std; 7 const int MAXN = 802+5; 8 const int MAXE = 201200+5; 9 10 int num; 11 int head[MAXN]; 12 struct node { 13 int v, flow; 14 int next; 15 } edge[MAXE]; 16 17 inline void add(int x, int y, int w) { 18 edge[num].v = y; 19 edge[num].flow = w; 20 edge[num].next = head[x]; 21 head[x] = num++; 22 } 23 24 int n, f, d; 25 int S, T; 26 27 int dis[MAXN], cur[MAXN]; 28 29 bool bfs() { 30 for(int i = 1; i <= T; ++i) dis[i] = 0; 31 dis[S] = 1; 32 queue<int> q; 33 q.push(S); 34 while(!q.empty()) { 35 int u = q.front(); 36 q.pop(); 37 for(int i = head[u]; i != -1; i = edge[i].next) { 38 int v = edge[i].v; 39 if(!dis[v] && edge[i].flow) { 40 dis[v] = dis[u] + 1; 41 q.push(v); 42 } 43 } 44 } 45 return dis[T] != 0; 46 } 47 48 int dfs(int u, int f) { 49 if(u == T || (!f)) return f; 50 int flow = 0; 51 for(int& i = cur[u]; i != -1; i = edge[i].next) { 52 int v = edge[i].v; 53 if(dis[v] == dis[u] + 1) { 54 int di = dfs(v, min(f, edge[i].flow)); 55 if(di > 0) { 56 f -= di; 57 flow += di; 58 edge[i].flow -= di; 59 edge[i^1].flow += di; 60 if(!f) break; 61 } 62 } 63 } 64 if(!flow) dis[u] = -1; 65 return flow; 66 } 67 68 int Dinic() { 69 int ans = 0; 70 while(bfs()) { 71 for(int i = 1; i <= T; ++i) cur[i] = head[i]; 72 ans += dfs(S, INF); 73 } 74 return ans; 75 } 76 77 int main() { 78 while(scanf("%d%d%d", &n, &f, &d) == 3) { 79 S = 1; T = f+n*2+d+2; 80 num = 0; 81 for(int i = 1; i <= T; ++i) head[i] = -1; 82 int x; 83 for(int i = 0; i != f; ++i) { 84 scanf("%d", &x); 85 add(1, 2+i, x); 86 add(2+i, 1, 0); 87 } 88 for(int i = 0; i != d; ++i) { 89 scanf("%d", &x); 90 add(2+f+n*2+i, T, x); 91 add(T, 2+f+n*2+i, 0); 92 } 93 char bin[400]; 94 for(int p = 0; p != n; ++p) { 95 scanf("%s", bin); 96 for(int i = 0; i != f; ++i) { 97 if(bin[i] == 'Y') { 98 add(2+i, 2+f+p, 1); 99 add(2+f+p, 2+i, 0); 100 } 101 } 102 } 103 for(int i = 2+f; i <= 1+f+n; ++i) { 104 add(i, i+n, 1); 105 add(i+n, i, 0); 106 } 107 for(int p = 0; p != n; ++p) { 108 scanf("%s", bin); 109 for(int i = 0; i != d; ++i) { 110 if(bin[i] == 'Y') { 111 add(2+f+n+p, 2+f+n*2+i, 1); 112 add(2+f+n*2+i, 2+f+n+p, 0); 113 } 114 } 115 } 116 printf("%d\n", Dinic()); 117 } 118 return 0; 119 }
// hdu 4289 最小割最大流定理
1 /* 2 * @Promlem: 3 * @Time Limit: ms 4 * @Memory Limit: k 5 * @Author: pupil-XJ 6 * @Date: 2019-11-14 23:38:16 7 * @LastEditTime: 2019-11-15 00:12:20 8 */ 9 #include<cstdio> 10 #include<algorithm> 11 #define INF 0x3f3f3f3f 12 using namespace std; 13 const int MAXN = 400+5; 14 const int MAXE = 80400+5; 15 16 int num; 17 int head[MAXN]; 18 struct node { 19 int v, flow; 20 int next; 21 } edge[MAXE]; 22 23 inline void add(int x, int y, int w) { 24 edge[num].v = y; 25 edge[num].flow = w; 26 edge[num].next = head[x]; 27 head[x] = num++; 28 } 29 30 int n, m; 31 int S, T; 32 int cost[MAXN]; 33 34 int dis[MAXN], cur[MAXN]; 35 36 int q[MAXN], l, r; 37 bool bfs() { 38 for(int i = 1; i <= n*2; ++i) dis[i] = 0; 39 dis[S] = 1; 40 q[1] = S; 41 l = r = 1; 42 while(l <= r) { 43 int u = q[l++]; 44 for(int i = head[u]; i != -1; i = edge[i].next) { 45 int v = edge[i].v; 46 if(!dis[v] && edge[i].flow) { 47 dis[v] = dis[u] + 1; 48 q[++r] = v; 49 } 50 } 51 } 52 return dis[T]; 53 } 54 55 int dfs(int u, int f) { 56 if(u == T || (!f)) return f; 57 int flow = 0; 58 for(int& i = cur[u]; i != -1; i = edge[i].next) { 59 int v = edge[i].v; 60 if(dis[v] == dis[u] + 1) { 61 int di = dfs(v, min(f, edge[i].flow)); 62 if(di) { 63 f -= di; 64 flow += di; 65 edge[i].flow -= di; 66 edge[i^1].flow += di; 67 if(!f) break; 68 } 69 } 70 } 71 if(!flow) dis[u] = -1; 72 return flow; 73 } 74 75 int Dinic() { 76 int ans = 0; 77 while(bfs()) { 78 for(int i = 1; i <= n*2; ++i) cur[i] = head[i]; 79 ans += dfs(S, INF); 80 } 81 return ans; 82 } 83 84 int main() { 85 while(scanf("%d%d", &n, &m) == 2) { 86 scanf("%d%d", &S, &T); 87 T = T + n; 88 num = 0; 89 for(int i = 1; i <= n*2; ++i) head[i] = -1; 90 for(int i = 1; i <= n; ++i) scanf("%d", &cost[i]); 91 for(int i = 1; i <= n; ++i) { 92 add(i, i+n, cost[i]); 93 add(i+n, i, 0); 94 } 95 int x, y; 96 for(int i = 0; i != m; ++i) { 97 scanf("%d%d", &x, &y); 98 add(x+n, y, INF); 99 add(y, x+n, 0); 100 add(y+n, x, INF); 101 add(x, y+n, 0); 102 } 103 printf("%d\n", Dinic()); 104 } 105 return 0; 106 }
// uva 10480 最小割集合
1 /* 2 * @Promlem: 3 * @Time Limit: ms 4 * @Memory Limit: k 5 * @Author: pupil-XJ 6 * @Date: 2019-11-15 00:24:15 7 * @LastEditTime: 2019-11-15 01:14:42 8 */ 9 #include<cstdio> 10 #include<algorithm> 11 #define INF 0x3f3f3f3f 12 using namespace std; 13 const int MAXN = 50+5; 14 const int MAXE = 1000+5; 15 16 int num; 17 int head[MAXN]; 18 struct node { 19 int u, v, flow; 20 int next; 21 } edge[MAXE]; 22 23 inline void add(int x, int y, int w) { 24 edge[num].u = x; 25 edge[num].v = y; 26 edge[num].flow = w; 27 edge[num].next = head[x]; 28 head[x] = num++; 29 } 30 31 int n, m; 32 33 int dis[MAXN], cur[MAXN]; 34 35 int q[MAXN], l, r; 36 bool bfs() { 37 for(int i = 1; i <= n; ++i) dis[i] = 0; 38 dis[1] = 1; 39 q[1] = 1; 40 l = r = 1; 41 while(l <= r) { 42 int u = q[l++]; 43 for(int i = head[u]; i != -1; i = edge[i].next) { 44 int v = edge[i].v; 45 if(!dis[v] && edge[i].flow) { 46 dis[v] = dis[u] + 1; 47 q[++r] = v; 48 } 49 } 50 } 51 return dis[2]; 52 } 53 54 int dfs(int u, int f) { 55 if(u == 2 || (!f)) return f; 56 int flow = 0; 57 for(int& i = cur[u]; i != -1; i = edge[i].next) { 58 int v = edge[i].v; 59 if(dis[v] == dis[u] + 1) { 60 int di = dfs(v, min(f, edge[i].flow)); 61 if(di) { 62 f -= di; 63 flow += di; 64 edge[i].flow -= di; 65 edge[i^1].flow += di; 66 if(!f) break; 67 } 68 } 69 } 70 if(!flow) dis[u] = -1; 71 return flow; 72 } 73 74 void Dinic() { 75 while(bfs()) { 76 for(int i = 1; i <= n; ++i) cur[i] = head[i]; 77 dfs(1, INF); 78 } 79 } 80 81 bool vis[MAXN]; 82 void color(int u) { 83 vis[u] = true; 84 for(int i = head[u]; i != -1; i = edge[i].next) { 85 int v = edge[i].v; 86 if(!vis[v] && edge[i].flow) color(v); 87 } 88 } 89 90 int main() { 91 while(scanf("%d%d", &n, &m) == 2 && n) { 92 num = 0; 93 for(int i = 1; i <= n; ++i) head[i] = -1; 94 int x, y, w; 95 for(int i = 0; i != m; ++i) { 96 scanf("%d%d%d", &x, &y, &w); 97 add(x, y, w); 98 add(y, x, w); 99 } 100 Dinic(); 101 for(int i = 1; i <= n; ++i) vis[i] = false; 102 color(1); 103 for(int u = 1; u <= n; ++u) { 104 for(int i = head[u]; i != -1; i = edge[i].next) { 105 int v = edge[i].v; 106 if(vis[u] && !vis[v]) printf("%d %d\n", u, v); 107 } 108 } 109 printf("\n"); 110 } 111 return 0; 112 }
// hdu 2732 最大流 水
1 /* 2 * @Promlem: 3 * @Time Limit: ms 4 * @Memory Limit: k 5 * @Author: pupil-XJ 6 * @Date: 2019-11-15 08:50:24 7 * @LastEditTime: 2019-11-15 10:51:36 8 */ 9 #include<cstdio> 10 #include<cstring> 11 #include<algorithm> 12 #define INF 0x3f3f3f3f 13 using namespace std; 14 const int MAXN = 80000; 15 const int MAXE = 800000; 16 17 int num; 18 int head[MAXN]; 19 struct node { 20 int v, flow; 21 int next; 22 } edge[MAXE]; 23 24 inline void add(int x, int y, int w) { 25 edge[num].v = y; 26 edge[num].flow = w; 27 edge[num].next = head[x]; 28 head[x] = num++; 29 } 30 31 int r, c, d; 32 int n, S, T, sum; 33 char A[102][102], B[102][102]; 34 35 void draw() { 36 for(int i = 0; i != r; ++i) { 37 for(int j = 0; j != c; ++j) { 38 if(A[i][j] == '0') continue; 39 add(i*c+j+1, i*c+j+1+n, A[i][j]-'0'); 40 add(i*c+j+1+n, i*c+j+1, 0); 41 if(B[i][j] == 'L') { 42 add(S, i*c+j+1, 1); 43 add(i*c+j+1, S, 0); 44 ++sum; 45 } 46 if(i-d<0 || i+d>=r || j-d<0 || j+d>=c) { 47 add(i*c+j+1+n, T, INF); 48 add(T, i*c+j+1+n, 0); 49 } 50 for(int ii = 0; ii <= i; ++ii) { 51 int cc = c-1; 52 if(ii == i) cc = j; 53 for(int jj = 0; jj <= cc; ++jj) { 54 if(ii == i && jj == j || A[ii][jj] == '0') continue; 55 if(abs(i-ii)+abs(j-jj) <= d) { 56 add(i*c+j+1+n, ii*c+jj+1, INF); 57 add(ii*c+jj+1, i*c+j+1+n, 0); 58 add(ii*c+jj+1+n, i*c+j+1, INF); 59 add(i*c+j+1, ii*c+jj+1+n, 0); 60 } 61 } 62 } 63 } 64 } 65 } 66 67 int dis[MAXN], cur[MAXN]; 68 69 int q[MAXN], ll, rr; 70 bool bfs() { 71 for(int i = 0; i <= T; ++i) dis[i] = 0; 72 dis[S] = 1; 73 q[1] = S; 74 ll = rr = 1; 75 while(ll <= rr) { 76 int u = q[ll++]; 77 for(int i = head[u]; i != -1; i = edge[i].next) { 78 int v = edge[i].v; 79 if(!dis[v] && edge[i].flow) { 80 dis[v] = dis[u] + 1; 81 q[++rr] = v; 82 } 83 } 84 } 85 return dis[T]; 86 } 87 88 int dfs(int u, int f) { 89 if(u == T || (!f)) return f; 90 int flow = 0; 91 for(int &i = cur[u]; i != -1; i = edge[i].next) { 92 int v = edge[i].v; 93 if(dis[v] == dis[u] + 1) { 94 int di = dfs(v, min(f, edge[i].flow)); 95 if(di) { 96 f -= di; 97 flow += di; 98 edge[i].flow -= di; 99 edge[i^1].flow += di; 100 if(!f) break; 101 } 102 } 103 } 104 if(!flow) dis[u] = -1; 105 return flow; 106 } 107 108 int Dinic() { 109 int ans = 0; 110 while(bfs()) { 111 for(int i = 0; i <= T; ++i) cur[i] = head[i]; 112 ans += dfs(S, INF); 113 } 114 return sum - ans; 115 } 116 117 int main() { 118 int qaq, QAQ = 0; 119 scanf("%d", &qaq); 120 while(qaq--) { 121 scanf("%d%d", &r, &d); 122 for(int i = 0; i != r; ++i) scanf("%s", A[i]); 123 for(int i = 0; i != r; ++i) scanf("%s", B[i]); 124 125 c = strlen(A[0]); 126 n = r*c; 127 S = 0; T = n*2+1; 128 num = sum = 0; 129 for(int i = 0; i <= T; ++i) head[i] = -1; 130 draw(); 131 int ans = Dinic(); 132 if(!ans) printf("Case #%d: no lizard was left behind.\n", ++QAQ); 133 else if(ans == 1) printf("Case #%d: 1 lizard was left behind.\n", ++QAQ); 134 else printf("Case #%d: %d lizards were left behind.\n", ++QAQ, ans); 135 } 136 return 0; 137 }
// hdu 3338 最大流 (巧妙建图)
1 #include<cstdio> 2 #include<algorithm> 3 #define INF 0x3f3f3f3f 4 using namespace std; 5 const int MAXN = 800000+5; 6 const int MAXE = 8000000+5; 7 8 int num; 9 int head[MAXN]; 10 struct node { 11 int v, flow; 12 int next; 13 } edge[MAXE]; 14 15 inline void add(int x, int y, int w) { 16 edge[num].v = y; 17 edge[num].flow = w; 18 edge[num].next = head[x]; 19 head[x] = num++; 20 } 21 22 int r, c; 23 char G[105][105][10]; 24 int e_num[105][105]; 25 int n, S, T; 26 27 void draw() { 28 for(int i = 1; i <= r; ++i) { 29 for(int j = 1; j <= c; ++j) { 30 if(G[i][j][0] == 'X' && G[i][j][4] == 'X') continue; 31 if(G[i][j][0] != '.') { 32 if(G[i][j][0] != 'X') { 33 int f = (G[i][j][0]-'0')*100+(G[i][j][1]-'0')*10+(G[i][j][2]-'0'); 34 int rr = i+1; 35 while(rr <= r && G[rr][j][0] == '.') { 36 add((i-1)*c+j, n+(rr-1)*c+j, 8); 37 e_num[rr][j] = num; 38 add(n+(rr-1)*c+j, (i-1)*c+j, 0); 39 ++rr; 40 f -= 1; 41 } 42 add(S, (i-1)*c+j, f); 43 add((i-1)*c+j, S, 0); 44 } 45 if(G[i][j][4] != 'X') { 46 int f = (G[i][j][4]-'0')*100+(G[i][j][5]-'0')*10+(G[i][j][6]-'0'); 47 int cc = j+1; 48 while(cc <= c && G[i][cc][0] == '.') { 49 add(n+(i-1)*c+cc, n*2+(i-1)*c+j, 8); 50 add(n*2+(i-1)*c+j, n+(i-1)*c+cc, 0); 51 ++cc; 52 f -= 1; 53 } 54 add(n*2+(i-1)*c+j, T, f); 55 add(T, n*2+(i-1)*c+j, 0); 56 } 57 } 58 } 59 } 60 } 61 62 int dis[MAXN], cur[MAXN]; 63 64 int q[MAXN], ll, rr; 65 bool bfs() { 66 for(int i = 0; i <= T; ++i) dis[i] = 0; 67 dis[S] = 1; 68 q[1] = 0; 69 ll = rr = 1; 70 while(ll <= rr) { 71 int u = q[ll++]; 72 for(int i = head[u]; i != -1; i = edge[i].next) { 73 int v = edge[i].v; 74 if(!dis[v] && edge[i].flow) { 75 dis[v] = dis[u] + 1; 76 q[++rr] = v; 77 } 78 } 79 } 80 return dis[T]; 81 } 82 83 int dfs(int u, int f) { 84 if(u == T || (!f)) return f; 85 int flow = 0; 86 for(int& i = cur[u]; i != -1; i = edge[i].next) { 87 int v = edge[i].v; 88 if(dis[v] == dis[u] + 1) { 89 int di = dfs(v, min(f, edge[i].flow)); 90 if(di) { 91 f -= di; 92 flow += di; 93 edge[i].flow -= di; 94 edge[i^1].flow += di; 95 if(!f) break; 96 } 97 } 98 } 99 if(!flow) dis[u] = -1; 100 return flow; 101 } 102 103 void Dinic() { 104 while(bfs()) { 105 for(int i = 0; i <= T; ++i) cur[i] = head[i]; 106 dfs(S, INF); 107 } 108 } 109 110 void solve() { 111 Dinic(); 112 int t; 113 for(int i = 1; i <= r; ++i) { 114 for(int j = 1; j <= c; ++j) { 115 if(j != 1) printf(" "); 116 if(G[i][j][0] != '.') printf("_"); 117 else printf("%d", edge[e_num[i][j]].flow+1); 118 } 119 printf("\n"); 120 } 121 } 122 123 int main() { 124 while(scanf("%d%d", &r, &c) == 2) { 125 n = r*c; 126 S = 0; T = 3*n+1; 127 num = 0; 128 for(int i = 0; i <= T; ++i) head[i] = -1; 129 for(int i = 1; i <= r; ++i) { 130 for(int j = 1; j <= c; ++j) { 131 scanf("%s", G[i][j]); 132 } 133 } 134 draw(); 135 solve(); 136 } 137 return 0; 138 }
// hdu 3605 多重匹配写的。
1 #include<cstdio> 2 #include<cstring> 3 #include<cmath> 4 #include<fstream> 5 #include<iostream> 6 #include<string> 7 #include<functional> 8 #include<algorithm> 9 #include<sstream> 10 #include<iomanip> 11 #include<vector> 12 #include<queue> 13 #include<stack> 14 #include<set> 15 #include<map> 16 #define read(n) n = read_n() 17 #define rep(i, n) for(int i=0;i!=n;++i) 18 #define per(i, n) for(int i=n-1;i>=0;--i) 19 #define Rep(i, sta, n) for(int i=sta;i!=n;++i) 20 #define rep1(i, n) for(int i=1;i<=n;++i) 21 #define per1(i, n) for(int i=n;i>=1;--i) 22 #define Rep1(i, sta, n) for(int i=sta;i<=n;++i) 23 #define L k<<1 24 #define R k<<1|1 25 #define mid (tree[k].l+tree[k].r)>>1 26 #define eps 1e-10 27 using namespace std; 28 const int INF = 0x3f3f3f3f; 29 typedef long long ll; 30 31 inline int read_n() { 32 char c=getchar();int x=0,f=1; 33 while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();} 34 while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();} 35 return x*f; 36 } 37 // ----------------------------------------------------- 38 const int MAXN = 100000+5; 39 const int MAXM = 10+5; 40 const int MAXE = MAXN*MAXM; 41 42 int num; 43 int head[MAXN]; 44 struct node { 45 int v, next; 46 } edge[MAXE]; 47 48 inline void add(int x, int y) { 49 edge[num].v = y; 50 edge[num].next = head[x]; 51 head[x] = num++; 52 } 53 54 int n, m; 55 int maxn[MAXM]; 56 57 int cnt[MAXM]; 58 int love[MAXM][MAXN]; 59 bool vis[MAXM]; 60 61 bool dfs(int u) { 62 for(int i = head[u]; i != -1; i = edge[i].next) { 63 int v = edge[i].v; 64 if(!vis[v]) { 65 vis[v] = true; 66 if(cnt[v] < maxn[v]) { 67 love[v][++cnt[v]] = u; 68 return true; 69 } 70 for(int j = 1; j <= cnt[v]; ++j) { 71 if(dfs(love[v][j])) { 72 love[v][j] = u; 73 return true; 74 } 75 } 76 } 77 } 78 return false; 79 } 80 81 bool solve() { 82 rep1(i, m) cnt[i] = 0; 83 rep1(i, n) { 84 rep1(j, m) vis[j] = false; 85 if(!dfs(i)) return false; 86 } 87 return true; 88 } 89 90 int main() { 91 while(cin >> n >> m) { 92 num = 0; 93 rep1(i, n) head[i] = -1; 94 int x; 95 rep1(i, n) rep1(j, m) { 96 read(x); 97 if(x == 1) add(i, j); 98 } 99 rep1(i, m) cin >> maxn[i]; 100 if(solve()) cout << "YES\n"; 101 else cout << "NO\n"; 102 } 103 return 0; 104 }
// hdu 3081 二分+并查集+最大流
1 #include<cstdio> 2 #include<cstring> 3 #include<algorithm> 4 #include<queue> 5 #define INF 0x3f3f3f3f 6 using namespace std; 7 const int MAXN = 205; 8 const int MAXE = 40005+5; 9 10 int num; 11 int head[MAXN]; 12 struct node { 13 int v, flow; 14 int next; 15 } edge[MAXE]; 16 17 inline void add(int x, int y, int w) { 18 edge[num].v = y; 19 edge[num].flow = w; 20 edge[num].next = head[x]; 21 head[x] = num++; 22 } 23 24 int n, m, f; 25 int fa[MAXN]; 26 bool vis[MAXN][MAXN], vis2[MAXN][MAXN]; 27 28 inline int find(int x) { return fa[x] == x ? x : fa[x] = find(fa[x]); } 29 30 void init() { 31 memset(vis, false, sizeof(vis)); 32 memset(vis2, false, sizeof(vis2)); 33 for(int i = 1; i <= n; ++i) fa[i] = i; 34 int x, y; 35 for(int i = 0; i != m; ++i) { 36 scanf("%d%d", &x, &y); 37 vis[x][y] = vis2[x][y] = true; 38 } 39 for(int i = 0; i != f; ++i) { 40 scanf("%d%d", &x, &y); 41 int xf = find(x), yf = find(y); 42 fa[xf] = yf; 43 } 44 } 45 46 int S, T; 47 int dis[MAXN], cur[MAXN]; 48 49 void draw(int f) { 50 S = 0; T = n*2+1; 51 num = 0; 52 for(int i = 0; i <= T; ++i) head[i] = -1; 53 for(int i = 1; i <= n; ++i) { 54 for(int j = 1; j <= n; ++j) { 55 vis[i][j] = vis2[i][j]; 56 } 57 } 58 59 for(int i = 1; i <= n; ++i) { 60 add(S, i, f); 61 add(i, S, 0); 62 add(n+i, T, f); 63 add(T, n+i, 0); 64 } 65 for(int i = 1; i <= n; ++i) { 66 for(int j = 1; j <= n; ++j) { 67 if(vis[i][j]) { 68 add(i, n+j, 1); 69 add(n+j, i, 0); 70 } 71 } 72 } 73 for(int i = 1; i <= n; ++i) { 74 for(int j = 1; j <= n; ++j) { 75 if(find(i) == find(j)) { 76 for(int k = 1; k <= n; ++k) { 77 if(vis[i][k] && !vis[j][k]) { 78 add(j, n+k, 1); 79 add(n+k, j, 0); 80 vis[j][k] = 1; 81 } 82 } 83 } 84 } 85 } 86 } 87 88 bool bfs() { 89 for(int i = 0; i <= T; ++i) dis[i] = 0; 90 dis[S] = 1; 91 queue<int> q; 92 q.push(S); 93 while(!q.empty()) { 94 int u = q.front(); 95 q.pop(); 96 for(int i = head[u]; i != -1; i = edge[i].next) { 97 int v = edge[i].v; 98 if(!dis[v] && edge[i].flow) { 99 dis[v] = dis[u] + 1; 100 q.push(v); 101 } 102 } 103 } 104 return dis[T]; 105 } 106 107 int dfs(int u, int f) { 108 if(u == T || (!f)) return f; 109 int flow = 0; 110 for(int& i = cur[u]; i != -1; i = edge[i].next) { 111 int v = edge[i].v; 112 if(dis[v] == dis[u] + 1) { 113 int di = dfs(v, min(f, edge[i].flow)); 114 if(di) { 115 f -= di; 116 flow += di; 117 edge[i].flow -= di; 118 edge[i^1].flow += di; 119 if(!f) break; 120 } 121 } 122 } 123 if(!flow) dis[u] = -1; 124 return flow; 125 } 126 127 int Dinic(int k) { 128 draw(k); 129 int ans = 0; 130 while(bfs()) { 131 for(int i = 0; i <= T; ++i) cur[i] = head[i]; 132 ans += dfs(S, INF); 133 } 134 return ans == n*k; 135 } 136 137 int main() { 138 int qaq; 139 scanf("%d", &qaq); 140 while(qaq--) { 141 scanf("%d%d%d", &n, &m, &f); 142 init(); 143 int l = 0, r = n; 144 int ans = 0; 145 while(l <= r) { 146 int mid = (l+r)>>1; 147 if(Dinic(mid)) l = mid + 1, ans = mid; 148 else r = mid - 1; 149 } 150 printf("%d\n", ans); 151 } 152 return 0; 153 }
// hdu 3416 最短路+最大流
1 #include<cstdio> 2 #include<cstring> 3 #include<algorithm> 4 #include<stack> 5 #define INF 0x3f3f3f3f 6 using namespace std; 7 const int MAXN = 1088+5; 8 const int MAXE = 800088+5; 9 10 int num1; 11 int head1[MAXN]; 12 struct node1 { 13 int v, w; 14 int next; 15 } e1[MAXE]; 16 17 inline void add1(int x, int y, int w) { 18 e1[num1].v = y; 19 e1[num1].w = w; 20 e1[num1].next = head1[x]; 21 head1[x] = num1++; 22 } 23 //--------------------------- 24 int num2; 25 int head2[MAXN]; 26 struct node2 { 27 int v, w; 28 int next; 29 } e2[MAXE]; 30 31 inline void add2(int x, int y, int w) { 32 e2[num2].v = y; 33 e2[num2].w = w; 34 e2[num2].next = head2[x]; 35 head2[x] = num2++; 36 } 37 //------------------------------- 38 int num; 39 int head[MAXN]; 40 struct node { 41 int v, flow; 42 int next; 43 } edge[MAXE]; 44 45 inline void add(int x, int y, int w) { 46 edge[num].v = y; 47 edge[num].flow = w; 48 edge[num].next = head[x]; 49 head[x] = num++; 50 } 51 //------------------------------------- 52 int n, m; 53 int S, T; 54 int d; 55 int dis2[MAXN]; 56 bool vis[MAXN]; 57 int d1[MAXN], d2[MAXN]; 58 59 void SPFA1(int s) { 60 for(int i = 1; i <= n; ++i) dis2[i] = INF, vis[i] = false; 61 dis2[s] = 0; 62 vis[s] = 1; 63 stack<int> q; 64 q.push(s); 65 while(!q.empty()) { 66 int u = q.top(); 67 q.pop(); 68 vis[u] = false; 69 for(int i = head1[u]; i != -1; i = e1[i].next) { 70 int v = e1[i].v; 71 if(dis2[v] > dis2[u] + e1[i].w) { 72 dis2[v] = dis2[u] + e1[i].w; 73 if(!vis[v]) { 74 vis[v] = true; 75 q.push(v); 76 } 77 } 78 } 79 } 80 } 81 82 void SPFA2(int s) { 83 for(int i = 1; i <= n; ++i) dis2[i] = INF, vis[i] = false; 84 dis2[s] = 0; 85 vis[s] = 1; 86 stack<int> q; 87 q.push(s); 88 while(!q.empty()) { 89 int u = q.top(); 90 q.pop(); 91 vis[u] = false; 92 for(int i = head2[u]; i != -1; i = e2[i].next) { 93 int v = e2[i].v; 94 if(dis2[v] > dis2[u] + e2[i].w) { 95 dis2[v] = dis2[u] + e2[i].w; 96 if(!vis[v]) { 97 vis[v] = true; 98 q.push(v); 99 } 100 } 101 } 102 } 103 } 104 105 void init() { 106 num1 = 0; 107 for(int i = 1; i <= n; ++i) head1[i] = -1; 108 int s, e, w; 109 for(int i = 0; i != m; ++i) { 110 scanf("%d%d%d", &s, &e, &w); 111 add1(s, e, w); 112 } 113 scanf("%d%d", &S, &T); 114 } 115 116 void draw() { 117 memcpy(d1, dis2, sizeof(dis2)); 118 num2 = 0; 119 for(int i = 1; i <= n; ++i) head2[i] = -1; 120 for(int u = 1; u <= n; ++u) { 121 for(int i = head1[u]; i != -1; i = e1[i].next) { 122 int v = e1[i].v; 123 add2(v, u, e1[i].w); 124 } 125 } 126 SPFA2(T); 127 memcpy(d2, dis2, sizeof(dis2)); 128 num = 0; 129 for(int i = 1; i <= n; ++i) head[i] = -1; 130 for(int u = 1; u <= n; ++u) { 131 for(int i = head1[u]; i != -1; i = e1[i].next) { 132 int v = e1[i].v; 133 if(d1[u] + e1[i].w + d2[v] == d) { 134 add(u, v, 1); 135 add(v, u, 0); 136 } 137 } 138 } 139 } 140 141 int dis[MAXN], cur[MAXN]; 142 int q[MAXN], ll, rr; 143 144 bool bfs() { 145 for(int i = 1; i <= n; ++i) dis[i] = 0; 146 dis[S] = 1; 147 q[1] = S; 148 ll = rr = 1; 149 while(ll <= rr) { 150 int u = q[ll++]; 151 for(int i = head[u]; i != -1; i = edge[i].next) { 152 int v = edge[i].v; 153 if(!dis[v] && edge[i].flow) { 154 dis[v] = dis[u] + 1; 155 q[++rr] = v; 156 } 157 } 158 } 159 return dis[T]; 160 } 161 162 int dfs(int u, int f) { 163 if(u == T || (!f)) return f; 164 int flow = 0; 165 for(int& i = cur[u]; i != -1; i = edge[i].next) { 166 int v = edge[i].v; 167 if(dis[v] == dis[u] + 1) { 168 int di = dfs(v, min(f, edge[i].flow)); 169 if(di) { 170 f -= di; 171 flow += di; 172 edge[i].flow -= di; 173 edge[i^1].flow += di; 174 if(!f) break; 175 } 176 } 177 } 178 if(!flow) dis[u] = -1; 179 return flow; 180 } 181 182 int Dinic() { 183 int ans = 0; 184 while(bfs()) { 185 for(int i = 1; i <= n; ++i) cur[i] = head[i]; 186 ans += dfs(S, INF); 187 } 188 return ans; 189 } 190 191 int main() { 192 int qaq; 193 scanf("%d", &qaq); 194 while(qaq--) { 195 scanf("%d%d", &n, &m); 196 init(); 197 SPFA1(S); 198 if(dis2[T] != INF) d = dis2[T]; 199 else { 200 printf("0\n"); 201 continue; 202 } 203 draw(); 204 printf("%d\n", Dinic()); 205 } 206 return 0; 207 }
