费用流模板

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

using namespace std;

const int N = 5010, M = 100010, inf = 1e8;

int n, m, S, T;
int h[N], e[M], ne[M], f[M], w[M], idx;
int pre[N], d[N], incf[N];
bool st[N];

void add(int a, int b, int c, int d)
{
    e[idx] = b, f[idx] = c, w[idx] = d, ne[idx] = h[a], h[a] = idx ++;
    e[idx] = a, f[idx] = 0, w[idx] = -d, ne[idx] = h[b], h[b] = idx ++;
}

bool spfa()
{
    memset(d, 0x3f, sizeof(d));
    memset(incf, 0, sizeof(incf));
    queue<int> que;
    que.push(S);
    d[S] = 0, incf[S] = inf;
    st[S] = true;
    while(que.size()) {
        int t = que.front();
        que.pop();
        st[t] = false;
        for(int i = h[t]; ~i; i = ne[i]) {
            int ver = e[i];
            if(d[ver] > d[t] + w[i] && f[i]) {
                d[ver] = d[t] + w[i];
                pre[ver] = i;
                incf[ver] = min(f[i], incf[t]);
                if(!st[ver]) {
                    que.push(ver);
                    st[ver] = true;
                }
            }
        }
    }
    return incf[T] > 0;
}

void EK(int &flow, int &cost)
{
    flow = 0, cost = 0;
    while(spfa()) {
        int t = incf[T];
        flow += t, cost += t * d[T];
        for(int i = T; i != S; i = e[pre[i] ^ 1]) {
            f[pre[i]] -= t;
            f[pre[i] ^ 1] += t;
        }
    }
}

int main()
{
    scanf("%d%d%d%d", &n, &m, &S, &T);
    memset(h, -1, sizeof(h));
    while(m --) {
        int a, b, c, d;
        scanf("%d%d%d%d", &a, &b, &c, &d);
        add(a, b, c, d);
    }
    int flow, cost;
    EK(flow, cost);
    printf("%d %d
", flow, cost);
    return 0;
}