poj1273:Drainage Ditches

最大流模板题~

#include<cstdio>
#include<iostream>
#include<string.h>
#define INF 100000000
using namespace std;

const int MAXN=10005;
struct node
{
    int v,f;
    node *next,*rev;       
}pool[MAXN],*h[MAXN];
int cnt,S,T;
int que[MAXN],level[MAXN],st,ed;
void addedge(int u,int v,int len)
{
    node *p=&pool[++cnt],*q=&pool[++cnt];
    p->v=v;p->next=h[u];h[u]=p;p->f=len;p->rev=q;
    q->v=u;q->next=h[v];h[v]=q;q->f=0;q->rev=p;   
}
bool make_level()
{
    int u,v;
    st=ed=0;
    for(int i=1;i<=T;i++) level[i]=-1;
    que[ed++]=S;level[S]=1;
    while(st<ed)
    {
        u=que[st++];
        for(node *p=h[u];p;p=p->next)
            if(p->f && level[v=p->v]==-1)
            {
                level[v]=level[u]+1;
                que[ed++]=v;
                if(level[T]!=-1) return true; 
            }
    }
    return false;
}
int find(int u,int k)
{
    if(u==T) return k;
    int s=0,t,v;
    for(node *p=h[u];p;p=p->next)
        if(s<k && level[v=p->v]==level[u]+1 && p->f)
        {
            t=find(v,min(k-s,p->f));
            if(t)
            {
                s+=t;
                p->f-=t;
                p->rev->f+=t;     
            }
        }
    if(s==0) level[u]=-1;
    return s;
}
int dinic()
{
    int ret=0;
    while(make_level()) ret+=find(S,INF);
    return ret;    
}

int main()
{
    int m,n,i,a,b,c;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        S=1;T=m;
        memset(h,NULL,sizeof(h));
        memset(pool,0,sizeof(pool));cnt=0;
        for(i=0;i<n;i++) scanf("%d%d%d",&a,&b,&c),addedge(a,b,c);
        printf("%d
",dinic());              
    }
    return 0;    
}