zkw费用流

//zkw费用流
#include <cstdio>
#include <iostream>
#include <cstring>

using namespace std;
const int MAXN = 20000 + 5;
const int INF = 0x7f7f7f7f;
int from[MAXN << 1], to[MAXN << 1], next[MAXN << 1], cap[MAXN << 1], cos[MAXN << 1];
int a[MAXN], q[MAXN], p[MAXN], d[MAXN], fst[MAXN], inq[MAXN];
int ecnt = 1;

inline void add(int f, int t, int c, int cc) {
    from[++ecnt] = f;
    to[ecnt] = t;
    cap[ecnt] = c;
    cos[ecnt] = cc;
    next[ecnt] = fst[f];
    fst[f] = ecnt;
}

int main() {
    int s, t, n, m;
    scanf("%d%d", &m, &n);
    s = 1;
    t = n;
    for (int i = 1; i <= m; i++) {
        int a, b, c, d;
        scanf("%d%d%d%d", &a, &b, &c, &d);
        add(a, b, c, d);
        add(b, a, 0, -d);
    }
    int flow = 0, cost = 0;
    while (true) {
        memset(d, 0x7f, sizeof(d));
        memset(inq, 0, sizeof(inq));
        d[s] = 0;
        inq[s] = 1;
        p[s] = 0;
        a[s] = INF;
        int head = 0, tail = 0, cnt = 0;
        q[tail++] = s;
        while (head < tail) {
            if (cnt > m)break;//minus circle
            int u = q[head++];
            inq[u] = 0;
            for (int i = fst[u]; i; i = next[i]) {
                if (cap[i] > 0 && d[to[i]] > d[u] + cos[i]) {
                    d[to[i]] = d[u] + cos[i];
                    p[to[i]] = i;
                    a[to[i]] = min(a[u], cap[i]);
                    if (!inq[to[i]]) {
                        q[tail++] = to[i];
                        inq[to[i]] = 1;
                    }
                }
            }
            cnt++;
        }
        if (d[t] >= INF)break;
        flow += a[t];
        cost += d[t] * a[t];
        for (int u = t; u != s; u = from[p[u]]) {
            cap[p[u]] -= a[t];
            cap[p[u] ^ 1] += a[t];
        }
    }
    printf("%d\n", cost);
    return 0;
}