网络流初步——增广路算法（EK）模板

#include <iostream>
#include <queue>
#include<string.h>
using namespace std;
#define arraysize 201
int maxData = 0x7fffffff;
int a[222][222];
int flow[222];
int pre[222];
int n,m;
queue<int> q;
int BFS(int s,int t)
{
    int i,j;
    while(!q.empty())
        q.pop();
    for(i=1;i<m+1;i++)
    {
        pre[i]=-1;
    }
    pre[s]=0;
    flow[s]= maxData;
    q.push(s);
    while(!q.empty())
    {
        int index=q.front();
        q.pop();
        if(index==t)
            break;
        for(i=1;i<m+1;++i)
        {
            if(i!=s && a[index][i]>0 && pre[i]==-1)
            {
                 pre[i]=index;
                 flow[i]=min(a[index][i],flow[index]);
                 q.push(i);
            }
        }
    }
    if(pre[t]==-1)
        return -1;
    else
        return flow[t];
}
int ek(int s,int t)
{
    int increasement=0;
    int sumflow=0;
    while((increasement=BFS(s,t))!=-1)
    {
         int k=t;
         while(k!=s)
         {
              int last=pre[k];
              a[last][k]-=increasement;
              a[k][last]+=increasement;
              k = last;
         }
         sumflow+=increasement;
    }
    return sumflow;
}
int main()
{
    int i,j;
    int start,end,ci;
    cin>>n>>m;
    memset(a,0,sizeof(a));
    memset(flow,0,sizeof(flow));
    for(i=0;i<n;i++)
    {
        cin>>start>>end>>ci;
        a[start][end]+=ci;
    }
    cout<<ek(1,m)<<endl;
    return 0;
}