最小费用最大流

#include <bits/stdc++.h>

using namespace std;
const int maxn=100010;
const int inf=0x3f3f3f3f;
typedef pair<int,int> PI;
struct MCFC {
    struct edge {
        int to, next, cap, flow, cost;
    } e[maxn];
    int head[maxn], tol;
    int pre[maxn], dis[maxn];
    bool vis[maxn];
    int N;

    void init(int n) {
        N = n;
        tol = 1;
        memset(head, 0, sizeof(head));
    }

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

    bool spfa(int s, int t) {
        queue<int> q;
        for (int i = 0; i <= N; i++) {
            dis[i] = inf;
            vis[i] = false;
            pre[i] = -1;
        }
        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; i = e[i].next) {
                int v = e[i].to;
                if (e[i].cap > e[i].flow && dis[v] >dis[u] + e[i].cost) {
                    dis[v] = dis[u] + e[i].cost;
                    pre[v] = i;
                    if (!vis[v]) {
                        vis[v] = true;
                        q.push(v);
                    }
                }
            }
        }
        if (pre[t] == -1) return false;
        else return true;
    }

    int cost = 0;

    PI mcmf(int s, int t) {
        int flow = 0;
        cost = 0;
        while (spfa(s, t)) {
            int minn = inf;
            for (int i = pre[t]; i != -1; i = pre[e[i ^ 1].to]) {
                if (minn > e[i].cap - e[i].flow) {
                    minn = e[i].cap - e[i].flow;
                }
            }
            for (int i = pre[t]; i != -1; i = pre[e[i ^ 1].to]) {
                e[i].flow += minn;
                e[i ^ 1].flow -= minn;
                cost += e[i].cost * minn;
            }
            flow += minn;
        }
        return make_pair(cost,flow);
    }

} G;

int main() {
    int n,m,s,t;
    scanf("%d%d%d%d", &n, &m, &s, &t);
    G.init(n);
    for (int i = 1; i <= m; i++) {
        int u, v, w, f;
        scanf("%d%d%d%d", &u, &v, &w, &f);
        G.addedge(u, v, w, f);
    }
    PI ans=G.mcmf(s, t);
    printf("%d %d
",ans.second,ans.first);
}

　　

#include<bits/stdc++.h>

using namespace std;
typedef pair<int,int> PI;
const int maxn=5000;
const int inf=0x3f3f3f3f;
int a[maxn];


struct Min_Cost_Max_Flow{
    struct edge{
        int to,cap,cost,rev;
        edge(){};
        edge(int _to,int _cap,int _cost,int _rev):to(_to),cap(_cap),cost(_cost),rev(_rev){};
    };
    vector<edge>E[maxn];
    int h[maxn],n,d[maxn],preV[maxn],preE[maxn];
    void init(int n){
        this->n=n;
        for (int i=0;i<=n;i++){
            E[i].clear();
            h[i]=0;
        }
    }
    void add(int from,int to,int cap,int cost){
        E[from].push_back(edge(to,cap,cost,E[to].size()));
        E[to].push_back(edge(from,0,-cost,E[from].size()-1));
    }

    PI dijkstra(int s,int t,int f){
        int cost=0,flow=0;
        for (int i=0;i<=n;i++){
            h[i]=0;
        }
        while (f){
            priority_queue<PI,vector<PI>,greater<PI> >q;
            for (int i=0;i<=n;i++){
                d[i]=inf;
            }
            d[s]=0;
            q.push(make_pair(0,s));
            while (!q.empty()){
                PI now=q.top();
                q.pop();
                int v=now.second;
                if (d[v]<now.first){
                    continue;
                }
                for (int i=0;i<E[v].size();i++){
                    edge &e=E[v][i];
                    if (e.cap>0&&d[e.to]>d[v]+e.cost+h[v]-h[e.to]){
                        d[e.to]=d[v]+e.cost+h[v]-h[e.to];
                        preV[e.to]=v;
                        preE[e.to]=i;
                        q.push(make_pair(d[e.to],e.to));
                    }
                }
            }
            if (d[t]==inf)break;
            for (int i=0;i<=n;i++){
                h[i]+=d[i];
            }
            int d=f;
            for (int i=t;i!=s;i=preV[i]){
                d=min(d,E[preV[i]][preE[i]].cap);
            }
            f-=d;
            flow+=d;
            cost+=d*h[t];
            for (int i=t;i!=s;i=preV[i]){
                    edge &e=E[preV[i]][preE[i]];
                    e.cap-=d;
                    E[i][e.rev].cap+=d;
            }
        }
        return make_pair(flow,cost);
    }
}G;

int main() {
    int t,k,n;
    scanf("%d", &t);
    while (t--) {
        scanf("%d%d", &n, &k);
        for (int i = 1; i <= n; i++) {
            scanf("%d", &a[i]);
        }
        G.init(2*n+2);
        int S = 0, T = 2 * n + 2;
        G.add(S, n * 2 + 1, k, 0);
        for (int i = 1; i <= n; i++) {
            G.add(n * 2 + 1, i, 1, 0);
            G.add(i, n + i, 1, -a[i]);
            G.add(n + i, T, 1, 0);
        }
        for (int i = 1; i <= n; i++) {
            for (int j = i + 1; j <= n; j++) {
                if (a[i] <= a[j]) {
                    G.add(n + i, j, 1, 0);
                }
            }
        }
        PI ans=G.dijkstra(S,T,inf);
        printf("%d
",-ans.second);
    }
}