【模板】dinic

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
#include<algorithm>
#define inf 0x7fffffff
using namespace std;
const int N=110,M=1100;
struct E {int to,cap,flow,nxt;}edge[M*2];
int tot=2,idx[N],cur[N];
queue<int>q;
int dis[N];
bool vis[N];
int n,m,s,t;
void addedge(int from,int to,int cap,int flow){
    edge[tot].to=to;edge[tot].cap=cap;edge[tot].flow=flow;
    edge[tot].nxt=idx[from];idx[from]=tot++;
}
bool bfs(){
    memset(vis,0,sizeof(vis));
    memset(dis,0,sizeof(dis));
    q.push(s);vis[s]=1;dis[s]=1;
    while(!q.empty()){
        int x=q.front();q.pop();
        for(int t=idx[x];t;t=edge[t].nxt){
            E e=edge[t];
            if(!vis[e.to] && e.cap>e.flow){
                vis[e.to]=1;
                dis[e.to]=dis[x]+1;
                q.push(e.to);
            }
        }
    }
    return vis[t];
}
int dfs(int x,int a){
    if(x==t || a==0) return a;
    int flow=0,f;
    for(int &i=cur[x];i;i=edge[i].nxt){
        E &e=edge[i];
        if(dis[e.to]==dis[x]+1){
            f=dfs(e.to,min(e.cap-e.flow,a));
            if(f>0){
                edge[i].flow+=f;
                edge[i^1].flow-=f;
                flow+=f;a-=f;
                if(a==0) break;
            }
        }
    }
    return flow;
}
int Dinic(){
    int ret=0;
    while(bfs()){
        for(int i=1;i<=n;i++) cur[i]=idx[i];
        ret+=dfs(s,inf);
    }
    return ret;
}
int main(){
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
    scanf("%d%d%d%d",&n,&m,&s,&t);
    for(int i=1;i<=m;i++){
        int x,y,w;
        scanf("%d%d%d",&x,&y,&w);
        addedge(x,y,w,0);addedge(y,x,0,0);
    }
    printf("%d\n",Dinic());
    return 0;
}