HDU3549(Flow Problem)(网络最大流)

赤裸裸的Ford-Fulkerson算法求最大流。

#include <iostream>
#include <cstring>
#include <queue>

using namespace std;
const int MAX = 1003;
int map[MAX][MAX],pre[MAX],n,m,ans;
bool vis[MAX];

int Maxflow()　　　　//　　采用BFS找增广路径
{
    while(true)
    {
        queue<int> que;
        memset(pre,0,sizeof(pre));
        memset(vis,0,sizeof(vis));
        vis[1] = true;     que.push(1);

        while(!que.empty())
        {
            int cur = que.front(); que.pop();

            if(cur == n) break;　　//　　表明已找到一条增广路径

            for(int i = 1;i <= n;++i)
            {
                if(!vis[i] && map[cur][i])
                {
                    que.push(i);  pre[i] = cur;
                    vis[i] = true;
                }
            }
        }

        if(!vis[n]) break;　　　　//　　无法找到增广路径

        int Min = 100000000;

        for(int u = n;u != 1;u = pre[u])
        {
            if(Min > map[pre[u]][u]) Min = map[pre[u]][u];
        }

        for(u = n;u != 1;u = pre[u])
        {
            map[pre[u]][u] -= Min;
            map[u][pre[u]] += Min;
        }
        ans += Min;
    }

    return ans;
}


int main()
{
    //freopen("hdu.txt","r",stdin);
    int u,v,d,t,i,j;

    cin>>t;

    for(int ca = 1;ca <= t;++ca)
    {
    //    cin>>n>>m;
        scanf("%d %d",&n,&m);

        for(i = 1;i <= n;++i)
        {
            for(j = 1;j <= n;++j)  map[i][j] = 0;
        }

        for(i = 0;i < m;++i)
        {
        //    cin>>u>>v>>d;
            scanf("%d %d %d",&u,&v,&d);
            map[u][v] += d;
        }

        ans = 0;
        Maxflow();

        cout<<"Case "<<ca<<": "<<ans<<endl;
    }

    return 0;
}