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#include<set> #include<map> #include<queue> #include<stack> #include<cmath> #include<string> #include<time.h> #include<vector> #include<cstdio> #include<cstring> #include<iostream> #include<algorithm> #define INF 1000000001 #define ll long long #define lson l,m,rt<<1 #define rson m+1,r,rt<<1|1 using namespace std; const int MAXN = 1010; struct node { int to; int val; int next; }edge[MAXN*100*2],e[MAXN*200*5]; int ind,pre[MAXN],vis[MAXN],dis[MAXN],pre1[MAXN],ind1; int now[MAXN],S,T; int n,m; void add1(int x,int y,int z) { e[ind1].to = y; e[ind1].val = z; e[ind1].next = pre1[x]; pre1[x] = ind1 ++; } void spfa() { for(int i = 1; i <= n; i++){ dis[i] = INF; vis[i] = 0; } vis[T] = 1; dis[T] = 0; queue<int>q; q.push(T); while(!q.empty()){ int tp = q.front(); q.pop(); vis[tp] = 0; for(int i = pre1[tp]; i != -1; i = e[i].next){ int t = e[i].to; if(dis[t] > dis[tp] + e[i].val){ dis[t] = dis[tp] + e[i].val; if(!vis[t]){ vis[t] = 1; q.push(t); } } } } } void add(int x,int y,int z) { edge[ind].to = y; edge[ind].val = z; edge[ind].next = pre[x]; pre[x] = ind ++; } void dfs1(int rt) { vis[rt] = 1; if(rt == T)return ; for(int i = pre1[rt]; i != -1; i = e[i].next){ int t = e[i].to; if(now[rt] + dis[t] + e[i].val == dis[S]){ now[t] = now[rt] + e[i].val; add(rt,t,1); add(t,rt,0); if(!vis[t]){ dfs1(t); } } } } int bfs() { memset(vis,-1,sizeof(vis)); queue<int>q; vis[S] = 0; q.push(S); while(!q.empty()){ int tp = q.front(); q.pop(); for(int i = pre[tp]; i != -1; i = edge[i].next){ int t = edge[i].to; if(vis[t] == -1 && edge[i].val){ vis[t] = vis[tp] + 1; q.push(t); } } } if(vis[T] == -1)return 0; return 1; } int dfs(int rt,int low) { int used = 0; if(rt == T)return low; for(int i = pre[rt]; i != -1 && used < low; i = edge[i].next){ int t = edge[i].to; if(vis[t] == vis[rt] + 1 && edge[i].val){ int a = dfs(t,min(low-used,edge[i].val)); used += a; edge[i].val -= a; edge[i^1].val += a; } } if(used == 0)vis[rt] = -1; return used; } int x[MAXN*100],y[MAXN*100],z[MAXN*100]; void Init(int flag) { ind1 = 0; memset(pre1,-1,sizeof(pre1)); for(int i = 1; i <= m; i++){ if(!flag){ add1(y[i],x[i],z[i]); } else { add1(x[i],y[i],z[i]); } } } int main() { int t; scanf("%d",&t); while(t--){ scanf("%d%d",&n,&m); for(int i = 1; i <= m; i++){ scanf("%d%d%d",&x[i],&y[i],&z[i]); } Init(0); scanf("%d%d",&S,&T); spfa(); Init(1); ind = 0; memset(now,0,sizeof(now)); memset(pre,-1,sizeof(pre)); dfs1(S); int ans = 0; while(bfs()){ while(1){ int a = dfs(S,INF); if(!a)break; ans += a; } } printf("%d\n",ans); } return 0; }
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原文地址:http://www.cnblogs.com/sweat123/p/5466911.html