uva 820 Internet Bandwidth

就是最大流问题。用的EK。

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#define maxx 1000000000
#include<queue>
using namespace std;
int ans,n,p[1000],a[1000],g[1000][1000];
int work(int s,int t)
{
  ans=0;
  while (true)
  {
    queue<int>q;
      for (int i=1;i<=n;i++) a[i]=0,p[i]=0;
      a[s]=maxx;
      q.push(s);
      while (!q.empty())
      {
        int now=q.front();q.pop();
        for (int i=1;i<=n;i++)
        if ((a[i]==0)&&(g[now][i]>0))
        {
          a[i]=min(a[now],g[now][i]);
        p[i]=now;
        q.push(i);    
      }
      if (a[t]) break;
    }
    if (!a[t]) break;
    ans+=a[t];
    for (int i=t;i!=s;i=p[i])
    {
      g[p[i]][i]-=a[t];
      g[i][p[i]]+=a[t];
    }
  }
  return ans;
}
int main()
{
  scanf("%d",&n);
  int tot=0;
  while (n!=0)
  {
    int st,en,m;
    scanf("%d%d%d",&st,&en,&m);
    for (int i=1;i<=n;i++)
    for (int j=1;j<=n;j++)
    g[i][j]=0;
    int x,y,z;
    for (int i=1;i<=m;i++)
    {
      scanf("%d%d%d",&x,&y,&z);
      g[x][y]+=z; g[y][x]+=z;
    }
    tot++;
    printf("Network %d\n",tot);
    printf("The bandwidth is %d.\n",work(st,en));
    cout<<endl;
    scanf("%d",&n);
  }
  return 0;
}