poj 1273 Drainage Ditches_最大流模版

#include <iostream>
#include<cstdio>
#include<queue>
#include<cstring>
using namespace std;
 #define INF 0xfffffff
 #define N 210
 int cap[N][N],flow[N][N];
 int pre[N],dist[N];
 int ek(int sta,int end){
 	int i,curr,sum=0;
 	memset(flow,0,sizeof(flow));
 	while(1){
 		memset(pre,0,sizeof(pre));
 		memset(dist,0,sizeof(dist));
 		queue<int> q;
 		q.push(sta);
 		dist[sta]=INF;
 		pre[sta]=sta;
 		while(!q.empty()){
 			curr=q.front();
 			q.pop();
 			for(i=1;i<=end;i++)
 				if(!dist[i]&&flow[curr][i]<cap[curr][i]){
 					dist[i]=min(dist[curr],cap[curr][i]-flow[curr][i]);
 					pre[i]=curr;
 					q.push(i);
 				}
 		}
 		if(dist[end]==0)
 			break;
 		for(i=end;i!=sta;i=pre[i]){
 			curr=pre[i];
 			flow[curr][i]+=dist[end];
 			flow[i][curr]-=dist[end];
 		}
 		sum+=dist[end];
 	}
 	return sum;
 }

int main(int argc, char** argv) {
	int n,m,i,a,b,w;
	while(scanf("%d%d",&n,&m)!=EOF){
		memset(cap,0,sizeof(cap));
		for(i=1;i<=n;i++){
			scanf("%d%d%d",&a,&b,&w);
			cap[a][b]+=w;
		}
		printf("%d\n",ek(1,m));
	}
	return 0;
}

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
#define N 210
#define INF 0xfffffff
int flow[N][N],dist[N],m,n;
int bfs(){
	memset(dist,-1,sizeof(dist));
	dist[1]=0;
	queue<int> q;
	q.push(1);
	while(!q.empty()){
		int k=q.front();
		q.pop();
		for(int i=1;i<=n;i++){
			if(flow[k][i]>0&&dist[i]<0){
				dist[i]=dist[k]+1;
				q.push(i);
			}
		}
	}
	if(dist[n]>0) return 1;
	else return 0;
}
int dfs(int x,int mx){
	int i,a;
	if(x==n) return mx;
	for(i=1;i<=n;i++){
		if(flow[x][i]>0&&dist[i]==dist[x]+1&&(a=dfs(i,min(mx,flow[x][i])))){
			flow[x][i]-=a;
			flow[i][x]+=a;
			return a;
		}

	}
	return 0;
}
int main(){
	int i,b,a,w,ans,res;
	while(scanf("%d%d",&m,&n)!=EOF){
		memset(flow,0,sizeof(flow));
		for(i=0;i<m;i++){
			scanf("%d%d%d",&a,&b,&w);
			flow[a][b]+=w;
		}
		ans=0;
		while(bfs())
			while(res=dfs(1,INF))
				ans+=res;
		printf("%d\n",ans);
	}
}