UVA-820 Internet Bandwidth （最大流）

题目大意：单源单汇无向网络求最大流。

题目分析：入门级别的题。但是ISAP在这儿好像不大好使？。。。

 

代码如下：

# include<iostream>
# include<cstdio>
# include<cstring>
# include<vector>
# include<queue>
# include<algorithm>
using namespace std;

const int INF=1<<30;
const int maxn=105;

int p[maxn],g[maxn][maxn];
int s,t,n,m;

int bfs()
{
    memset(p,-1,sizeof(p));
    p[s]=s;
    queue<int>q;
    q.push(s);
    while(!q.empty())
    {
        int u=q.front();
        q.pop();
        for(int i=0;i<n;++i){
            if(g[u][i]>0&&p[i]==-1){
                p[i]=u;
                q.push(i);
            }
        }
    }
    if(p[t]==-1) return 0;
    int a=INF,u=t;
    while(p[u]!=u){
        a=min(a,g[p[u]][u]);
        u=p[u];
    }
    u=t;
    while(p[u]!=u){
        g[p[u]][u]-=a;
        g[u][p[u]]+=a;
        u=p[u];
    }
    return a;
}

int maxFlow()
{
    int flow=0,f;
    while(1){
        f=bfs();
        if(f<=0) break;
        flow+=f;
    }
    return flow;
}

int main()
{
    int a,b,c,cas=0;
    while(scanf("%d",&n)&&n)
    {
        scanf("%d%d%d",&s,&t,&m);
        --s,--t;
        memset(g,0,sizeof(g));
        while(m--)
        {
            scanf("%d%d%d",&a,&b,&c);
            --a,--b;
            g[a][b]+=c;
            g[b][a]+=c;
        }
        printf("Network %d\n",++cas);
        printf("The bandwidth is %d.\n\n",maxFlow());
    }
    return 0;
}