[HDOJ5889]Barricade(spfa,最大流)
题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=5889
求出所有最短路,标记好以后跑最大流就是最小割。
1 #include <bits/stdc++.h> 2 using namespace std; 3 #define fr first 4 #define sc second 5 #define cl clear 6 #define BUG puts("here!!!") 7 #define W(a) while(a--) 8 #define pb(a) push_back(a) 9 #define Rint(a) scanf("%d", &a) 10 #define Rll(a) scanf("%lld", &a) 11 #define Rs(a) scanf("%s", a) 12 #define Cin(a) cin >> a 13 #define FRead() freopen("in", "r", stdin) 14 #define FWrite() freopen("out", "w", stdout) 15 #define Rep(i, len) for(int i = 0; i < (len); i++) 16 #define For(i, a, len) for(int i = (a); i < (len); i++) 17 #define Cls(a) memset((a), 0, sizeof(a)) 18 #define Clr(a, x) memset((a), (x), sizeof(a)) 19 #define Full(a) memset((a), 0x7f7f7f, sizeof(a)) 20 #define lrt rt << 1 21 #define rrt rt << 1 | 1 22 #define pi 3.14159265359 23 #define RT return 24 #define lowbit(x) x & (-x) 25 #define onenum(x) __builtin_popcount(x) 26 typedef long long LL; 27 typedef long double LD; 28 typedef unsigned long long ULL; 29 typedef pair<int, int> pii; 30 typedef pair<string, int> psi; 31 typedef pair<LL, LL> pll; 32 typedef map<string, int> msi; 33 typedef vector<int> vi; 34 typedef vector<LL> vl; 35 typedef vector<vl> vvl; 36 typedef vector<bool> vb; 37 38 const int maxn = 1100; 39 const int maxm = 11000; 40 const int inf = 1000000000; 41 typedef struct Edge { 42 int u, v, w; 43 int next; 44 Edge() { next = -1; } 45 }Edge; 46 47 int n, m, s, t; 48 Edge edge[maxm]; 49 int head[maxn], ecnt; 50 int d[maxn]; 51 bool vis[maxn]; 52 int u, v, w; 53 54 int cnt, dhead[maxn]; 55 int cur[maxn], dd[maxn]; 56 Edge dedge[maxm]; 57 int S, T, N; 58 59 void adde(int u, int v, int w) { 60 edge[ecnt].u = u; edge[ecnt].v = v; edge[ecnt].w = w; 61 edge[ecnt].next = head[u]; head[u] = ecnt++; 62 } 63 64 void init() { 65 Clr(head, -1); ecnt = 0; Cls(vis); 66 Cls(edge); 67 Clr(dhead, -1); Cls(dedge); 68 cnt = 0; 69 } 70 71 void spfa(int s) { 72 queue<int> q; 73 Rep(i, n+1) d[i] = inf; 74 d[s] = 0; q.push(s); 75 vis[s] = 1; 76 while(!q.empty()) { 77 int u = q.front(); q.pop(); vis[u] = 0; 78 for(int i = head[u]; ~i; i=edge[i].next) { 79 int v = edge[i].v; 80 if(d[v] > d[u] + 1) { 81 d[v] = d[u] + 1; 82 if(!vis[v]) { 83 vis[v] = 1; 84 q.push(v); 85 } 86 } 87 } 88 } 89 } 90 91 void dadde(int u, int v, int w, int c1) { 92 dedge[cnt].u = u; dedge[cnt].v = v; dedge[cnt].w = w; 93 dedge[cnt].next = dhead[u]; dhead[u] = cnt++; 94 dedge[cnt].u = v; dedge[cnt].v = u; dedge[cnt].w = c1; 95 dedge[cnt].next = dhead[v]; dhead[v] = cnt++; 96 } 97 98 bool bfs(int s, int t, int n) { 99 queue<int> q; 100 for(int i = 0; i < n; i++) dd[i] = inf; 101 dd[s] = 0; 102 q.push(s); 103 while(!q.empty()) { 104 int u = q.front(); q.pop(); 105 for(int i = dhead[u]; ~i; i = dedge[i].next) { 106 if(dd[dedge[i].v] > dd[u] + 1 && dedge[i].w > 0) { 107 dd[dedge[i].v] = dd[u] + 1; 108 if(dedge[i].v == t) return 1; 109 q.push(dedge[i].v); 110 } 111 } 112 } 113 return 0; 114 } 115 116 int dinic(int s, int t, int n) { 117 int st[maxn], top; 118 int u; 119 int flow = 0; 120 while(bfs(s, t, n)) { 121 for(int i = 0; i < n; i++) cur[i] = dhead[i]; 122 u = s; top = 0; 123 while(cur[s] != -1) { 124 if(u == t) { 125 int tp = inf; 126 for(int i = top - 1; i >= 0; i--) { 127 tp = min(tp, dedge[st[i]].w); 128 } 129 flow += tp; 130 for(int i = top - 1; i >= 0; i--) { 131 dedge[st[i]].w -= tp; 132 dedge[st[i] ^ 1].w += tp; 133 if(dedge[st[i]].w == 0) top = i; 134 } 135 u = dedge[st[top]].u; 136 } 137 else if(cur[u] != -1 && dedge[cur[u]].w > 0 && dd[u] + 1 == dd[dedge[cur[u]].v]) { 138 st[top++] = cur[u]; 139 u = dedge[cur[u]].v; 140 } 141 else { 142 while(u != s && cur[u] == -1) { 143 u = dedge[st[--top]].u; 144 } 145 cur[u] = dedge[cur[u]].next; 146 } 147 } 148 } 149 return flow; 150 } 151 152 signed main() { 153 //FRead(); 154 int ttt; 155 Rint(ttt); 156 W(ttt) { 157 init(); 158 Rint(n); Rint(m); 159 Rep(i, m) { 160 Rint(u); Rint(v); Rint(w); 161 adde(u,v,w); adde(v,u,w); 162 } 163 spfa(1); 164 Rep(i, ecmt) { 165 if(d[edge[i].v] == d[edge[i].u] + 1) { 166 dadde(edge[i].u-1, edge[i].v-1, edge[i].w, 0); 167 } 168 } 169 S = 0; T = n - 1; N = n; 170 printf("%d\n", dinic(S, T, N)); 171 } 172 RT 0; 173 }