poj 1273 Drainage Ditches

也是一道模板题目...敲一遍熟悉熟悉

 

#include <iostream>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <vector>
#include <set>
#include <queue>
#include <stack>
#include <climits>//形如INT_MAX一类的
#define MAX 205
#define INF 0x7FFFFFFF
# define eps 1e-5
//#pragma comment(linker, "/STACK:36777216") ///传说中的外挂
using namespace std;

int cap[MAX][MAX],pre[MAX],flow[MAX];
int m,n;

int bfs(int s,int e)
{
    queue<int >q;
    memset(pre,-1,sizeof(pre));
    pre[s] = 0;
    flow[s] = INF;
    q.push(s);
    while(! q.empty())
    {
        int t = q.front();
        q.pop();
        if(t == e)
            break;
        for(int i=1; i<=m; i++)
        {
            if(pre[i] == -1 && cap[t][i] > 0 )
            {
                q.push(i);
                pre[i] = t;
                flow[i] = min(flow[t],cap[t][i]);
            }
        }
    }
    if(pre[e] == -1)
        return -1;
    return flow[e];
}

int maxflow(int s,int e)
{
    int imp=0;
    int sum=0;
    while((imp = bfs(s,e)) != -1)
    {
        int ind = e;
        while(ind != s)
        {
            cap[pre[ind]][ind] -= imp;
            cap[ind][pre[ind]] += imp;
            ind = pre[ind];
        }
        sum += imp;
    }
    return sum;
}

void init()
{
    memset(cap,0,sizeof(cap));
    memset(flow,0,sizeof(flow));
}

int main()
{
    int a,b,c;
    while(scanf("%d%d",&n,&m) != EOF)
    {
        init();
        for(int i=0; i<n; i++)
        {
            scanf("%d%d%d",&a,&b,&c);
            if(a == b)
                continue;
            cap[a][b] += c;
        }
        printf("%d\n",maxflow(1,m));
    }
    return 0;
}