最小费用最大流

#include<iostream>
#include<queue>
#include<cstring>
using namespace std;
#define N 512
#define inf 0x7fffffff
int n,m,x,y,ca,c;
struct maxFlowMinCost{
	int cap[N][N],cost[N][N];
	int pre[N],dis[N];
	int n,m,ans,s,t;
	queue<int>q;
	bool inQue[N];
	void input(){
		cin>>n>>m;
		memset(cost,0x7f,sizeof(cost));
		for(int i=1;i<=n;i++)cost[i][i]=0;
		for(int i=1;i<=m;i++){
			cin>>x>>y>>ca>>c;
			cap[x][y]=ca;
			cost[x][y]=c;
		}
		s=1,t=n;
	}
	bool spfa(){
		memset(pre,-1,sizeof(pre));
		memset(inQue,0,sizeof(inQue));
		fill(dis,dis+N,inf);
		dis[s]=0;
		q.push(s);
		while(!q.empty()){
			int v=q.front();
			q.pop();
			inQue[v]=0;
			for(int i=1;i<=n;i++){
				if(cap[v][i]>0&&dis[i]>dis[v]+cost[v][i]){
					if(!inQue[i]){
						q.push(i);
						inQue[i]=1;
					}
					dis[i]=dis[v]+cost[v][i];
					pre[i]=v;
				}
			}
		}
		return dis[t]^inf;
	}
	int excute(){
		input();
		int minCost=0,maxFlow=0;
		while(spfa()){
			int neck=inf;
			for(int i=t;i!=s;i=pre[i])
				neck=min(neck,cap[pre[i]][i]);
			maxFlow+=neck;
			for(int i=t;i!=s;i=pre[i]){
				cap[pre[i]][i]-=neck;
				cap[i][pre[i]]+=neck;
				cost[i][pre[i]]=-cost[pre[i]][i];
				minCost+=cost[pre[i]][i]*neck;
			}
		}
		return minCost;
	}
}mcmf;
int main(){
	cout<<mcmf.excute();
}