poj 1273 最大流入门

明天再拍一遍

 #include <iostream>
 #include <queue>
 using namespace std;
 const int N = ;
 const int INF = 0x7FFFFFFF;
 int n,m,map[N][N],path[N],flow[N],start,end;
 queue<int> q;
 int bfs()
 {
     int i,t;
     while(!q.empty()) q.pop();
     memset(path,-,sizeof(path));
     path[start]=,flow[start]=INF;
     q.push(start);
     while(!q.empty())
     {
         t=q.front();
         q.pop();
         if(t==end) break;
         for(i=;i<=m;i++)
         {
             if(i!=start && path[i]==- && map[t][i])
             {
                 flow[i]=flow[t]<map[t][i]?flow[t]:map[t][i];
                 q.push(i);
                 path[i]=t;
             }
         }
     }
     if(path[end]==-) return -;
     return flow[m];                   //一次遍历之后的流量增量
 }
 int Edmonds_Karp()
 {
     int max_flow=,step,now,pre;
     while((step=bfs())!=-)
     {          //找不到增路径时退出
         max_flow+=step;
         now=end;
         while(now!=start)
         {
             pre=path[now];
             map[pre][now]-=step;      //更新正向边的实际容量
             map[now][pre]+=step;      //添加反向边
             now=pre;
         }
     }
     return max_flow;
 }
  int main()
  {
     int i,u,v,cost;
     while(scanf("%d %d",&n,&m)!=EOF)
     {
         memset(map,,sizeof(map));
         for(i=;i<n;i++)
         {
             scanf("%d %d %d",&u,&v,&cost);
             map[u][v]+=cost;           //not just only one input
         }
         start=,end=m;
         printf("%d\n",Edmonds_Karp());
     }
     return ;
 }