HDU 1532 Drainage Ditches(Dinic)

网络流dinic模板:

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <queue>
#include<math.h>
#define inf 0x3f3f3f3f
#define ls l,mid,rt<<1
#define rs mid+1,r,rt<<1|1
#define maxn 10000000

using namespace std;

struct node
{
    int to,w,next;
} q[300000];
int head[300000],l[300000],cnt,s,e;
void bu(int a,int b,int c)
{
    q[cnt].to=b;
    q[cnt].w=c;
    q[cnt].next=head[a];
    head[a]=cnt++;

    q[cnt].to=a;
    q[cnt].next=head[b];
    q[cnt].w=0;
    head[b]=cnt++;
}
int bfs()
{
    queue<int >Q;
    while(!Q.empty())
        Q.pop();
    memset(l,-1,sizeof(l));
    l[s]=0;
    Q.push(s);
    while(!Q.empty())
    {
        int v=Q.front();
        Q.pop();
        for(int i=head[v]; ~i; i=q[i].next)
        {
            if(q[i].w>0&&l[q[i].to ]==-1)
            {
                l[q[i].to ]=l[v]+1;
                Q.push(q[i].to);
            }
        }
    }
    return l[e]!=-1;
}
int dfs(int x,int f)
{
    if(x==e)
    {
        return f;
    }
    int tmp=0,a;
    for(int i=head[x]; ~i; i=q[i].next)
    {
        if(q[i].w>0&&(l[q[i].to ]==l[x]+1 ))
        {
            if(a=dfs(q[i].to,min(q[i].w,f-tmp)))
            {
                q[i].w-=a;
                q[i^1].w+=a;
                tmp+=a;
            }
        }
    }
    if(tmp==0)
        l[x]=-1;
    return tmp;
}
int main()
{
    int n,m,i,j,k,cla,A=1;
    while(~scanf("%d%d",&m,&n))
    {
        int a,b,c;
        cnt=0;
        s=1,e=n;
        memset(head,-1,sizeof(head));
        for(i=0; i<m; i++)
        {
            scanf("%d%d%d",&a,&b,&c);
            bu(a,b,c);
        }
        int ans=0;
        while(bfs())
        {
            ans+=dfs(1,inf);
        }
        printf("%d\n",ans);
    }
    return 0;
}