最小费用最大流模板

const int INF = 0x3f3f3f3f;
const int MAXN = ; 
 
struct Edge{
	int value,flow,to,rev;
	Edge(){}
	Edge(int a,int b,int c,int d):to(a),value(b),flow(c),rev(d){}
};
 
vector<Edge> E[MAXN];
 
inline void Add(int from,int to,int flow,int value){
	E[from].push_back(Edge(to,value,flow,E[to].size()));
	E[to].push_back(Edge(from,-value,0,E[from].size()-1));
}
 
bool book[MAXN];//用于SPFA中标记是否在queue中 
int cost[MAXN];//存费用的最短路径 
int pre[MAXN];//存前节点 
int pree[MAXN];//存在前节点的vector中的下标 
 
bool Spfa(int from,int to){
	memset(book,false,sizeof book);
	memset(cost,INF,sizeof cost);
	book[from] = true;
	cost[from] = 0;
	queue<int> Q;
	Q.push(from);
	while(!Q.empty()){
		int t = Q.front();
		book[t] = false;
		Q.pop();
		for(int i=0 ; i<E[t].size() ; ++i){
			Edge& e = E[t][i];
			if(e.flow > 0 && cost[e.to] > cost[t] + e.value){
				cost[e.to] = cost[t] + e.value;
				pre[e.to] = t;
				pree[e.to] = i;
				if(book[e.to] == false){
					Q.push(e.to);
					book[e.to] = true;
				}
			}
		}
	}
	return cost[to] != INF;
}
 
int Work(int from,int to){
	int sum = 0;
	while(Spfa(from,to)){
		int mflow = INF;//SPFA找到的最短路径的最小容量 
		int flag = to;
		while(flag != from){
			mflow = min(mflow,E[pre[flag]][pree[flag]].flow);
			flag = pre[flag];
		}
		flag = to;
		while(flag != from){
			sum += E[pre[flag]][pree[flag]].value * mflow;
			E[pre[flag]][pree[flag]].flow -= mflow;
			E[flag][E[pre[flag]][pree[flag]].rev].flow += mflow;
			flag = pre[flag];
		}
	}
	return sum;//返回费用
}