图论——最小费用最大流

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <queue>
#include <cstring>
#define INF 0x3f3f3f3f
using namespace std;
struct edge{
   int from,to,cap,cost,next;
}E[600000];
int tot;
int head[300];int dis[300];
int inq[300];
int pre[300];
int maxf = 0;
void addedge(int a,int b,int cap, int cost)
{
    E[tot].from = a;
    E[tot].to = b;
    E[tot].cap = cap;
    E[tot].cost = cost;
    E[tot].next = head[a];
    head[a] = tot++;
    //反向边
    E[tot].from = b;
    E[tot].to = a;
    E[tot].cap = 0;
    E[tot].cost = -cost;
    E[tot].next = head[b];
    head[b] = tot++;
}
void init()
{
    memset(E,0,sizeof(E));
    memset(head,-1,sizeof(head));
    memset(pre,-1,sizeof(pre));
    tot = 0;
    maxf = 0;
}bool spfa(int b , int e)
{
    memset(dis,INF,sizeof(dis));
    memset(inq,false,sizeof(inq));
    memset(pre, -1, sizeof(pre));
    queue<int> q;
    dis[b] = 0;
    inq[b] = true;
    q.push(b);
    while (!q.empty())
    {
        int u = q.front() ;q.pop();
        for (int i = head[u]; i!=-1 ; i = E[i].next)
        {
            int v = E[i].to;
            if (E[i].cap && dis[v] > dis[u] + E[i].cost)
            {
                dis[v] = dis[u] + E[i].cost;
                pre[v] = i;
                if (!inq[v])
                    {q.push(v);inq[v] = true;}
            }
        }
        inq[u] = false;
    }
    return pre[e]!=-1;
}
int MCMF(int b ,int e)
{
    int ANS = 0;
    while (spfa(b,e))
    {

        int minf = INF;
        for (int i = e ; i!=b ; i = E[pre[i]].from)
        {
            minf = min(minf , E[pre[i]].cap);
        }
        for (int i = e ; i!=b ; i = E[pre[i]].from)
        {
            E[pre[i]].cap -= minf;
            E[pre[i]^1].cap += minf;
        }
        maxf += minf;
        ANS += (minf*dis[e]);
    }
    return ANS;
}
int main()
{
        initfirst();
        init();
        MCMF(b,e);

}