POJ_1273 Drainage Ditches (网络流)

　　/*很裸的网络流题目，看了两天算导，今天终于A了一道网络流的题目。我的第一道网络流啊。。。^ ^

My Code:*/

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>

using namespace std;

const int N = 210;
const int inf = 0x6fffffff;

bool vis[N];
int map[N][N];
int pre[N];
int n, m;

int augment() {
    int v, i, f_min;
    bool flag = false;

    memset(pre, 0, sizeof(pre));
    memset(vis, false, sizeof(vis));

    deque<int> q;
    q.push_back(1);
    pre[1] = 0;
    vis[1] = true;

    while(!q.empty()) {
        v = q.front();
        q.pop_front();
        for(i = 1; i <= m; i++) {
            if(map[v][i] > 0 && !vis[i]) {
                pre[i] = v;
                vis[i] = true;
                if(i == m) {
                    flag = true;
                    q.clear();
                    break;
                }
                else
                    q.push_back(i);
            }
        }
    }
    if(!flag)    return 0;
    v = m; f_min = inf;

    while(pre[v]) {
        f_min = map[pre[v]][v] < f_min ? map[pre[v]][v] : f_min;
        v = pre[v];
    }

    v = m;
    while(pre[v]) {
        map[pre[v]][v] -= f_min;
        map[v][pre[v]] += f_min;
        v = pre[v];
    }
    return f_min;
}

int main() {
    //freopen("data.in", "r", stdin);

    int ans, a, b, c, aug;

    while(~scanf("%d%d", &n, &m)) {
        memset(map, 0, sizeof(map));
        while(n--) {
            scanf("%d%d%d", &a, &b, &c);
            map[a][b] += c;
        }
        ans = 0; aug = augment();
        while(aug) {
            ans += aug;
            aug = augment();
        }
        printf("%d\n", ans);
    }
    return 0;
}