模板 - 图论 - 最小费用最大流

#include<bits/stdc++.h>
using namespace std;

const int MAXN=10000;
const int MAXM=100000;
const int INF=0x3f3f3f3f;
struct Edge{
    int to,next,cap,flow,cost;
}edge[MAXM];
int head[MAXN],tol;
int pre[MAXN],dis[MAXN];
bool vis[MAXN];

void init(){
    tol=0;
    memset(head,-1,sizeof(head));
}

void addedge(int u,int v,int cap,int cost){
    edge[tol].to=v;
    edge[tol].cap=cap;
    edge[tol].cost=cost;
    edge[tol].flow=0;
    edge[tol].next=head[u];
    head[u]=tol++;

    edge[tol].to=u;
    edge[tol].cap=0;
    edge[tol].cost=-cost;
    edge[tol].flow=0;
    edge[tol].next=head[v];
    head[v]=tol++;
}

bool spfa(int s,int t){
    queue<int> q;
    memset(dis,INF,sizeof(dis));
    memset(vis,false,sizeof(vis));
    memset(pre,-1,sizeof(pre));

    dis[s]=0;
    vis[s]=true;
    q.push(s);
    while(!q.empty()){
        int u=q.front();
        q.pop();
        vis[u]=false;
        for(int i=head[u];i!=-1;i=edge[i].next){
            int v=edge[i].to;
            if(edge[i].cap>edge[i].flow&&dis[v]>dis[u]+edge[i].cost){
                dis[v]=dis[u]+edge[i].cost;
                pre[v]=i;
                if(!vis[v]){
                    vis[v]=true;
                    q.push(v);
                }
            }
        }
    }
    if(pre[t]==-1)
        return false;
    else
        return true;
}

int minCostMaxFlow(int s,int t,int &cost){
    int flow=0;
    cost=0;
    while(spfa(s,t)){
        int Min=INF;
        for(int i=pre[t];i!=-1;i=pre[edge[i^1].to]){
            if(Min>edge[i].cap-edge[i].flow)
                Min=edge[i].cap-edge[i].flow;
        }
        for(int i=pre[t];i!=-1;i=pre[edge[i^1].to]){
            edge[i].flow+=Min;
            edge[i^1].flow-=Min;
            cost+=edge[i].cost*Min;
        }
        flow+=Min;
    }
    return flow;
}

int main(){
    int N,M,S,T;
    scanf("%d%d%d%d",&N,&M,&S,&T);
    init();
    while(M--){
        int u,v,cap,cost;
        scanf("%d%d%d%d",&u,&v,&cap,&cost);
        addedge(u,v,cap,cost);
    }
    int cost=0;
    int flow=minCostMaxFlow(S,T,cost);

    printf("%d %d\n",flow,cost);
}