POJ 1273&Dinic解决

题目链接 http://poj.org/problem?id=1273

#include<iostream>
using namespace std;
#include<queue>
#include<vector>
#include<cstring>
#include<algorithm>
#include<deque>
#define INFINITE 0x7fffff
int G[300][300];
bool Visited[300];
int Layer[300];
int n,m; //1是源点 m是汇点
bool CountLayer()
{
    int layer=0;
    deque<int>q;
    memset(Layer,0xff,sizeof(Layer));
    Layer[1]=0;
    q.push_back(1);
    while (!q.empty())
    {
        int v=q.front();
        q.pop_front();
        for (int j=1;j<=m;j++)
        {
            if (G[v][j]>0&&Layer[j]==-1)
            {
                Layer[j]=Layer[v]+1;
                if (j==m)
                    return true;
                else
                    q.push_back(j);
            }
        }
    }
    return false;
}
int Dinic()
{
    int i;
    int s;
    int nMaxFlow=0;
    deque<int>q;
    while (CountLayer())
    {
        q.push_back(1);
        memset(Visited,0,sizeof(Visited));
        Visited[1]=1;
        while (!q.empty())
        {
            int nd=q.back();
            if (nd==m)
            {
                //source
                int nMinC=INFINITE;
                int nMinC_vs;
                for (i=1;i<q.size();i++)
                {
                    int vs=q[i-1];
                    int ve=q[i];
                    if (G[vs][ve]>0)
                    {
                        if (nMinC>G[vs][ve])
                        {
                            nMinC=G[vs][ve];
                            nMinC_vs=vs;
                        }
                    }
                }
                nMaxFlow+=nMinC;
                for (i=1;i<q.size();i++)
                {
                    int vs=q[i-1];
                    int ve=q[i];
                    G[vs][ve]-=nMinC; //修改边容量
                    G[ve][vs]+=nMinC; //添加反向边
                }
                while (!q.empty()&&q.back()!=nMinC_vs)
                {
                    Visited[q.back()]=0;
                    q.pop_back();
                }
            }
            else
            {
                for (i=1;i<=m;i++)
                {
                    if (G[nd][i]>0&&Layer[i]==Layer[nd]+1&&!Visited[i])
                    {
                        Visited[i]=1;
                        q.push_back(i);
                        break;
                    }
                }
                if (i>m)
                    q.pop_back();
            }
        }
    }
    return nMaxFlow;
}
int main()
{
    while (cin>>n>>m)
    {
        int i,j,k;
        int s,e,c;
        memset(G,0,sizeof(G));
        for (int i=0;i<n;i++)
        {
            cin>>s>>e>>c;
            G[s][e]+=c;
        }
        cout<<Dinic()<<endl;
    }
    return 0;
}