MnZn 求助：玄学RE

RT，之前忘了开 ll 还得了 64 分，开完就全 RE 了……

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int inf=1e9,N=250;
int n,m,s,t,g[N][N],pre[N];
int bfs()  {
    int flow[N];
    memset(pre,-1,sizeof(pre));
    flow[s]=inf;pre[s]=0;
    queue<int>Q; Q.push(s);
    while(!Q.empty()) {
        int u=Q.front();Q.pop();
        if(u==t) break;
        for(int i=1;i<=m;++i)
            if(i^s&&g[u][i]&&pre[i]==-1) {
                pre[i]=u,Q.push(i);
                flow[i]=min(flow[u],g[u][i]);
            }
    }
    if(pre[t]==-1) return -1;
    return flow[t];
}
int mflow() {
    int Mflow=0;
    while(true) {
        int f=bfs();
        if(f==-1) break;
        int cur=t;
        while(cur^s) {
            int fa=pre[cur];
            g[fa][cur]-=f;
            g[cur][fa]+=f;
            cur=fa;
        }
        Mflow+=f;
    }
    return Mflow;
}
signed main(void) {
    scanf("%d%d%d%d",&n,&m,&s,&t);
    for(int i=0;i<m;++i) {
        int u,v,w;
        scanf("%d%d%lld",&u,&v,&w);
        g[u][v]+=w;
    }
    printf("%lld\n",mflow());
    return 0;
}