POJ 1273 Drainage Ditches

裸的网络流，不过可能有重边，要把容量相加

 

代码：

#include<iostream>using namespace std;int f[205][205],cap[205][205];int rc[205],pre[205],q[205];int n,m,ans;bool bfs(){int i,j,head=0,tail=1;memset(rc,0,sizeof(rc));pre[1]=-1;rc[1]=99999999;q[tail]=1;while(head<tail){i=q[++head];for(j=1;j<=m;j++){if(cap[i][j]>f[i][j]&&!rc[j]){rc[j]=rc[i];if(cap[i][j]-f[i][j]<rc[i])rc[j]=cap[i][j]-f[i][j];pre[j]=i;q[++tail]=j;if(j==m)return true;}}}return false;}void update(){for(int i=m;i!=1;i=pre[i]){f[pre[i]][i]+=rc[m];f[i][pre[i]]=-f[pre[i]][i];}ans+=rc[m];}void EK(){while(bfs())update();}int main(){int i,j,a,b,w;while(scanf("%d %d",&n,&m)!=EOF){memset(f,0,sizeof(f));memset(cap,0,sizeof(cap));for(i=1;i<=n;i++){scanf("%d %d %d",&a,&b,&w);cap[a][b]+=w;}ans=0;EK();printf("%d/n",ans);}return 0;}