POJ1273(网络流)

裸裸的最大流模板题。

/*Source Code
Problem: 1273  User: HEU_daoguang 
Memory: 704K  Time: 0MS 
Language: G++  Result: Accepted 
Source Code*/ 
#include <iostream>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
using namespace std;
int m,n;

#define V 250
#define E 400500
#define inf 10050000
struct Edge{
    int u,v,c,next;
}edge[E];
int cnt;
int dist[V];
int head[V];
int que[V];
int sta[V];

void init(){
    cnt=0;
    memset(head,-1,sizeof(head));
}

void addedge(int u,int v,int c){
    edge[cnt].u=u;edge[cnt].v=v;edge[cnt].c=c;
    edge[cnt].next=head[u];head[u]=cnt++;
    edge[cnt].u=v;edge[cnt].v=u;edge[cnt].c=0;
    edge[cnt].next=head[v];head[v]=cnt++;
}

int dinic(int s,int t){
    int ans=0;
    while(true){

        int left,right,u,v;
        memset(dist,-1,sizeof(dist));
        left=right=0;
        que[right++]=s;
        dist[s]=0;

        while(left<right){
            u=que[left++];
            for(int k=head[u];k!=-1;k=edge[k].next){
                u=edge[k].u;
                v=edge[k].v;
                if(edge[k].c>0 && dist[v]==-1){
                    dist[v]=dist[u]+1;
                    que[right++]=v;

                    if(v==t){
                        left=right;
                        break;
                    }
                }
            }

        }

        if(dist[t]==-1) break;

        int top=0;
        int now=s;
        while(true){
            if(now!=t){
                int k;
                for(k=head[now];k!=-1;k=edge[k].next){
                    if(edge[k].c>0 && dist[edge[k].v]==dist[edge[k].u]+1) break;
                }
                if(k!=-1){
                    sta[top++]=k;
                    now=edge[k].v;
                }
                else{
                    if(top==0) break;
                    dist[edge[sta[--top]].v]=-1;
                    now=edge[sta[top]].u;
                }
            }
            else{
                int flow=inf,ebreak;
                for(int i=0;i<top;i++){
                    if(flow>edge[sta[i]].c){
                        flow=edge[sta[i]].c;
                        ebreak=i;
                    }
                }
                ans+=flow;
                for(int i=0;i<top;i++){
                    edge[sta[i]].c-=flow;
                    edge[sta[i]^1].c+=flow;
                }
                now=edge[sta[ebreak]].u;
                top=ebreak;
            }
        }

    }
    return ans;
}

int main()
{
    int a,b,c;
    //freopen("in.txt","r",stdin);
    while(scanf("%d%d",&m,&n)!=EOF){
        init();
        for(int i=1;i<=m;i++){
            scanf("%d%d%d",&a,&b,&c);
            addedge(a,b,c);
        }
        printf("%d\n",dinic(1,n));
    }
    return 0;
}