HDU3549+FordFulkerson

Ford-Fulkerson算法

基本没什么技巧

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<queue>
using namespace std;
#define N 1005
#define inf 9999999
int map[N][N],pre[N],vis[N];
int start,eend,ans;

void max_flow(int n)
{
    int i,j,k;
    while(1)
    {
        queue<int>q;
        while(!q.empty())q.pop();

        memset(vis,0,sizeof(vis));
        //memset(pre,-1,sizeof(pre));

        q.push(start);
        vis[start]=1;
        while(!q.empty())
        {
            k=q.front();
            q.pop();
            if(k==eend) break;//找到了增广路
            for(i=1;i<=n;i++)
            {
                if(vis[i]==1||map[k][i]==0)continue;
                q.push(i);
                vis[i]=1;
                pre[i]=k;
            }
        }

        if(vis[eend]==0)break;//无法找到增广路

        int min=inf;
        for(i=eend;i!=start;i=pre[i])
        {
            if(map[pre[i]][i]<min)
            {
                min=map[pre[i]][i];
            }
        }

        for(i=eend;i!=start;i=pre[i])
        {
            map[pre[i]][i]-=min;
            map[i][pre[i]]+=min;
        }
        ans+=min;
    }
    return ;
}

int main()
{
    int i,j,k,tcase,t;
    int m,n,a,b,c;
    scanf("%d",&tcase);
    for(t=1;t<=tcase;t++)
    {
        scanf("%d%d",&n,&m);
        start=1;
        eend=n;
        memset(map,0,sizeof(map));
        while(m--)
        {
            scanf("%d%d%d",&a,&b,&c);
            map[a][b]+=c;
        }
        ans=0;
        max_flow(n);
        printf("Case %d: %d\n",t,ans);
    }
    return 0;
}