最小费用最大流spfa

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
#define mem(a,b) memset(a,b,sizeof(a))
using namespace std;
const int maxn = 100100, INF = 0x7fffffff;
int head[maxn], d[maxn], vis[maxn], p[maxn], f[maxn];
int n, m, s, t;
int flow, value;
struct node{
    int u, v, c, f, w, next;
}Node[maxn];

void add(int u, int v, int c, int f, int w, int i)
{
    Node[i].u = u;
    Node[i].v = v;
    Node[i].c = c;
    Node[i].f = f;
    Node[i].w = w;
    Node[i].next = head[u];
    head[u] = i;
}

int spfa()
{
    queue<int> Q;
    mem(vis,0);
    mem(p,-1);
    for(int i=0; i<=n; i++) d[i] = INF;
    d[s] = 0;
    Q.push(s);
    vis[s] = 1;
    p[s] = 0; f[s] = INF;
    while(!Q.empty())
    {
        int u = Q.front(); Q.pop();
        vis[u] = 0;
        for(int i=head[u]; i!=-1; i=Node[i].next)
        {
            node e = Node[i];
            if(d[e.v] > d[u] + e.w && e.c > e.f)
            {
                d[e.v] = d[u] + e.w;
                p[e.v] = i;
                f[e.v] = min(f[u], e.c - e.f);
                if(!vis[e.v])
                {
                    Q.push(e.v);
                    vis[e.v] = 1;
                }
            }
        }
    }
    if(p[t] == -1) return 0;
    flow += f[t]; value += f[t] * d[t];
    for(int i=t; i!=s; i=Node[p[i]].u)
    {
        Node[p[i]].f += f[t];
        Node[p[i]^1].f -= f[t];
    }
    return 1;
}

void max_flow()
{
    while(spfa());
    printf("%d %d
",flow,value);
}

int main()
{
    mem(head,-1);
    cin>> n >> m >> s >> t;
    int cnt = 0;
    flow = 0, value = 0;
    for(int i=0; i<m; i++)
    {
        int u, v, c, w;
        cin>> u >> v >> c >> w;
        add(u,v,c,0,w,cnt++);
        add(v,u,0,0,-w,cnt++);
    }
    max_flow();

    return 0;
}