UVA 820(p380)----Internet Bandwidth

#include<iostream>
#include<cstdio>
#include<queue>
#include<cstring>
#include<algorithm>
using namespace std;
const int inf=100000000;
const int maxn=500,maxm=500000;
struct edge
{
    int v,f,nxt;
};
int n,src,sink,m;
int g[maxn+50];
int num;
edge e[maxm*2+50];
queue<int> que;
bool vis[maxn+50];
int dist[maxn+10];
void addedge(int u,int v,int c)
{
    e[++num].v=v;
    e[num].f=c;
    e[num].nxt=g[u];
    g[u]=num;
    e[++num].v=u;
    e[num].f=0;
    e[num].nxt=g[v];
    g[v]=num;
    swap(u,v);
    e[++num].v=v;
    e[num].f=c;
    e[num].nxt=g[u];
    g[u]=num;
    e[++num].v=u;
    e[num].f=0;
    e[num].nxt=g[v];
    g[v]=num;

}
void init()
{
    memset(g,0,sizeof(g));
    num=1;
}
void bfs()
{
    memset(dist,0,sizeof(dist));
    while(!que.empty()) que.pop();
    vis[src]=true;
    que.push(src);
    while(!que.empty())
    {
        int u=que.front();
        que.pop();
        for(int i=g[u];i;i=e[i].nxt)
            if(e[i].f&&!vis[e[i].v])
              {
                  que.push(e[i].v);
                  dist[e[i].v]=dist[u]+1;
                  vis[e[i].v]=true;
              }
    }
}
int dfs(int u,int delta)
{
    if(u==sink) return delta;
    else
    {
        int ret=0;
        for(int i=g[u];delta&&i;i=e[i].nxt)
            if(e[i].f&&dist[e[i].v]==dist[u]+1)
              {
                  int dd=dfs(e[i].v,min(e[i].f,delta));
                  e[i].f-=dd;
                  e[i^1].f+=dd;
                  delta-=dd;
                  ret+=dd;
              }
        return ret;
    }
}
int maxflow()
{
    int ret=0;
    while(1)
    {
        memset(vis,0,sizeof(vis));
        bfs();
        if(!vis[sink]) return ret;
        ret+=dfs(src,inf);
    }
}

int main()
{
  // freopen("in.in","r",stdin);
  // freopen("out.out","w",stdout);
   int cas=0;
   while(scanf("%d",&n)!=EOF&&n)
   {
       init();cas++;
       scanf("%d%d%d",&src,&sink,&m);
       for(int i=0;i<m;i++)
       {
           int x,y,c;
           scanf("%d%d%d",&x,&y,&c);
           addedge(x,y,c);
       }
       printf("Network %d\n",cas);
       printf("The bandwidth is %d.\n\n",maxflow());
   }
   return 0;
}

题目地址：https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=761