HDU 1532 && POJ 1273 Drainage Ditches （网络流 EK算法）

#include<stdio.h>
#include<queue>
#include<iostream>
using namespace std;
#include<string.h>
#define MAXN 205
#define INF 0xfffffff
int map[MAXN][MAXN];
int pre[MAXN];
int vis[MAXN];
int m,n;
int bfs(int s,int t){
memset(pre,-1,sizeof(pre));
memset(vis,0,sizeof(vis));
queue<int > q;
q.push(s);
vis[s]=1;
pre[s]=s;
while(!q.empty()){
int now=q.front();
q.pop();
for(int i=1;i<=n;i++){
if(map[now][i]&&!vis[i]){
pre[i]=now;
vis[i]=1;
if(i==t)return 1;
q.push(i);
}
}
}
return 0;
}
int EK(int s,int t){
int i,d,flow=0;
while(bfs(s,t)){
d=INF;
for(i=t;i!=s;i=pre[i])
if(d>=map[pre[i]][i])
d=map[pre[i]][i];
for(i=t;i!=s;i=pre[i]){
map[pre[i]][i]-=d;
map[i][pre[i]]+=d;
}
flow+=d;
}
return flow;
}
int main(){
while(scanf("%d%d",&m,&n)!=EOF){
memset(map,0,sizeof(map));
int s,e,v;
for(int i=1;i<=m;i++){
scanf("%d%d%d",&s,&e,&v);
map[s][e]+=v;
}
printf("%d\n",EK(1,n));
}
return 0;
}