hdu1532 （最大流入门，EK算法）

看着这个博客 

然后敲了hdu1532这个入门题，算是对最大流有点理解了

#include <stdio.h>
#include <string.h>
#include <queue>
using namespace std;
const int INF = 1<<30;
const int N = 200 + 10;
int n,m;
int cap[N][N],flow[N],pre[N];
int bfs(int src, int des)//每次用bfs找到最小的delta
{
    queue<int> q;
    for(int i=1;i<=n; ++i)
        pre[i] = -1;
    pre[src] = 0;
    flow[src] = INF;
    q.push(src);
    while(!q.empty())
    {
        int u = q.front(); q.pop();
    
        for(int i=1;i<=n;++i)  
        if(i!=src && cap[u][i]>0 && pre[i]==-1)
        {
            pre[i] = u;
            flow[i] = min(cap[u][i],flow[u]);
            q.push(i);
        }
    }
    //printf("%d
",pre[des]);
    if(pre[des]==-1)
        return -1;
    else
        return flow[des];
}
int maxFlow(int src, int des)
{
    int sumFlow = 0;
    int add = 0;
    while((add = bfs(src,des)) != -1)//如果不为-1，那么就进行增广
    {
        int k = des;
        while(k!=src)
        {
            int fa = pre[k];
            cap[fa][k] -= add;
            cap[k][fa] += add;
            k = fa;
        }
        sumFlow += add;
    }
    return sumFlow;
    
}
int main()
{
    
    while(scanf("%d%d",&m,&n)!=EOF)
    {
        int u,v,c;
        memset(cap,0,sizeof(cap));
        for(int i=1;i<=m;++i)
        {
            scanf("%d%d%d",&u,&v,&c);
            cap[u][v] += c;

        }
        int ans = maxFlow(1,n);
        printf("%d
",ans);
    }
    return 0;
}