bzoj 3931 最短路+最大流
较水，但因为范围问题WA了两次。。。。
1 /************************************************************** 2 Problem: 3931 3 User: idy002 4 Language: C++ 5 Result: Accepted 6 Time:392 ms 7 Memory:3224 kb 8 ****************************************************************/ 9 10 #include <cstdio> 11 #include <cstring> 12 #include <vector> 13 #include <queue> 14 #define min(a,b) ((a)<(b)?(a):(b)) 15 #define N 1100 16 #define M 200010 17 #define oo 0x3f3f3f3f 18 using namespace std; 19 20 typedef long long dnt; 21 struct Pair { 22 int u; 23 dnt d; 24 Pair( int u, dnt d ):u(u),d(d){} 25 bool operator<( const Pair &p ) const { return d>p.d; } 26 }; 27 struct Edge { 28 int u, v, f; 29 Edge( int u, int v, int f ):u(u),v(v),f(f){} 30 }; 31 struct Dinic { 32 int src, dst; 33 vector<Edge> edge; 34 vector<int> g[N]; 35 int dep[N], cur[N], qu[N], bg, ed; 36 void init( int src, int dst ) { 37 this->src = src; 38 this->dst = dst; 39 } 40 void adde( int u, int v, int f ) { 41 g[u].push_back( edge.size() ); 42 edge.push_back( Edge(u,v,f) ); 43 g[v].push_back( edge.size() ); 44 edge.push_back( Edge(v,u,0) ); 45 } 46 bool bfs() { 47 memset( dep, 0, sizeof(dep) ); 48 qu[bg=ed=1] = src; 49 dep[src] = 1; 50 while( bg<=ed ) { 51 int u=qu[bg++]; 52 for( int t=0; t<g[u].size(); t++ ) { 53 Edge &e = edge[g[u][t]]; 54 if( e.f && !dep[e.v] ) { 55 dep[e.v] = dep[e.u]+1; 56 qu[++ed] = e.v; 57 } 58 } 59 } 60 return dep[dst]; 61 } 62 dnt dfs( int u, dnt a ) { 63 if( u==dst || a==0 ) return a; 64 dnt remain=a, past=0, na; 65 for( int &t=cur[u]; t<g[u].size(); t++ ) { 66 Edge &e = edge[g[u][t]]; 67 Edge &ve = edge[g[u][t]^1]; 68 if( e.f && dep[e.v]==dep[e.u]+1 && (na=dfs(e.v,min(remain,e.f))) ) { 69 remain -= na; 70 past += na; 71 e.f -= na; 72 ve.f += na; 73 if( !remain ) break; 74 } 75 } 76 return past; 77 } 78 dnt maxflow() { 79 dnt rt = 0; 80 while( bfs() ) { 81 memset( cur, 0, sizeof(cur) ); 82 rt += dfs(src,0x3f3f3f3f3f3f3f3fll); 83 } 84 return rt; 85 } 86 }D; 87 88 int n, m; 89 int head[N], cc[N], dest[M], wght[M], next[M], etot; 90 dnt dis[2][N]; 91 int in[N], out[N], src, dst, idc; 92 93 void adde( int u, int v, int w ) { 94 etot++; 95 dest[etot] = v; 96 wght[etot] = w; 97 next[etot] = head[u]; 98 head[u] = etot; 99 } 100 void dijstra( int src, dnt dis[] ) { 101 static bool done[N]; 102 memset( done, false, sizeof(done) ); 103 priority_queue<Pair> q; 104 q.push( Pair(src,0) ); 105 dis[src] = 0; 106 while( !q.empty() ) { 107 Pair p = q.top(); 108 q.pop(); 109 int u=p.u; 110 if( done[u] ) continue; 111 done[u] = true; 112 for( int t=head[u]; t; t=next[t] ) { 113 int v=dest[t], w=wght[t]; 114 if( dis[v]>dis[u]+w ) { 115 dis[v]=dis[u]+w; 116 q.push( Pair(v,dis[v]) ); 117 } 118 } 119 } 120 } 121 void makeid() { 122 idc = 0; 123 for( int i=1; i<=n; i++ ) { 124 in[i] = ++idc; 125 out[i] = ++idc; 126 } 127 src = out[1]; 128 dst = in[n]; 129 } 130 void build() { 131 memset( dis, 0x3f, sizeof(dis) ); 132 dijstra( 1, dis[0] ); 133 dijstra( n, dis[1] ); 134 makeid(); 135 D.init( src, dst ); 136 for( int i=1; i<=n; i++ ) 137 if( dis[0][n]==dis[0][i]+dis[1][i] ) 138 D.adde( in[i], out[i], cc[i] ); 139 for( int u=1; u<=n; u++ ) 140 for( int t=head[u]; t; t=next[t] ) { 141 int v=dest[t], w=wght[t]; 142 if( dis[0][u]+dis[1][v]+w==dis[0][n] ) 143 D.adde( out[u], in[v], oo ); 144 } 145 } 146 int main() { 147 scanf( "%d%d", &n, &m ); 148 for( int i=1,u,v,w; i<=m; i++ ) { 149 scanf( "%d%d%d", &u, &v, &w ); 150 adde( u, v, w ); 151 adde( v, u, w ); 152 } 153 for( int i=1; i<=n; i++ ) 154 scanf( "%d", cc+i ); 155 build(); 156 printf( "%lld\n", D.maxflow() ); 157 } 158
