spfa求图的最大流

题目链接：

https://vjudge.net/contest/255738#problem/B

AC代码：

#include <iostream>
#include<vector>
#include<string>
#include<cstring>
#include<queue>
#include<stdio.h>
#define maxn 2000+10
using namespace std;
#define inf 0x3f3f3f3f
int n,m;
vector<pair<int,int > >q[maxn];
int vis[maxn];
int  path[maxn];
int spfa()
{
    for(int i=1; i<=n; i++)
    {
        vis[i]=0;
        path[i]=0;
    }
    path[1]=inf;
    vis[1]=1;
    queue<int>w;
    w.push(1);
    int maxx=0;
    while(!w.empty())
    {
        int top=w.front();
        w.pop();
        vis[top]=0;
        maxx=max(maxx,path[n]);
        if(path[top]<maxx)continue;
        int len=q[top].size();
        for(int i=0; i<len; i++)
        {
            int temp=q[top][i].first;
            if(path[temp]<=path[top])
            if(path[temp]<min(path[top],q[top][i].second)){
            path[temp]=min(path[top],q[top][i].second);
            if(path[temp]>maxx&&vis[temp]==0)
                w.push(temp),vis[temp]=1;
            }
        }
    }
    return maxx;
}
int main()
{
    int T;
    int num=0;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d%d",&n,&m);
        //  cin>>n>>m;
        for(int i=1; i<=n; i++)q[i].clear();
        for(int i=1; i<=m; i++)
        {
            int u,v,w;
            scanf("%d%d%d",&u,&v,&w);
            q[u].push_back(make_pair(v,w));
            q[v].push_back(make_pair(u,w));
        }
        int ans=spfa();
        printf("Scenario #%d:\n",++num);
        printf("%d\n",ans);
        printf("\n");
        // cout<<"Scenario #"<<++num<<":"<<endl<<ans<<endl;
    }
    return 0;
}