BZOJ 4873 寿司餐厅（最大权闭合图 网络流）

#include <bits/stdc++.h>
#define inf 0x3f3f3f3f
#define met(a,b) memset(a,b,sizeof a)
#define pb push_back
#define mp make_pair
#define inf 0x3f3f3f3f
using namespace std;
typedef long long ll;
const int N = 1e5+50;
const int mod = 1e9+7;
const double pi= acos(-1.0);
typedef pair<int,int>pii;
int n,m,k,f;
int a[150],d[150][150],An=1000;
int num[150][150],cnt,ans;
struct Edge{
    int from,to,cap,flow;
    Edge(int u,int v,int c,int f):from(u),to(v),cap(c),flow(f){}
};
struct Dinic{
    int s,t;
    vector<Edge>edges;
    vector<int> G[N];
    bool vis[N];
    int d[N];
    int cur[N];
    void init(){
       for (int i=0;i<=n+1;i++)
           G[i].clear();
       edges.clear();
    }
    void AddEdge(int from,int to,int cap){
        edges.push_back(Edge(from,to,cap,0));
        edges.push_back(Edge(to,from,0,0));
        int mm=edges.size();
        G[from].push_back(mm-2);
        G[to].push_back(mm-1);
    }
    bool BFS(){
        memset(vis,0,sizeof(vis));
        queue<int>q;
        q.push(s);
        d[s]=0;
        vis[s]=1;
        while (!q.empty()){
            int x = q.front();q.pop();
            for (int i = 0;i<G[x].size();i++){
                Edge &e = edges[G[x][i]];
                if (!vis[e.to] && e.cap > e.flow){
                    vis[e.to]=1;
                    d[e.to] = d[x]+1;
                    q.push(e.to);
                }
            }
        }
        return vis[t];
    }
 
    int DFS(int x,int a){
        if (x==t || a==0)
            return a;
        int flow = 0,f;
        for(int &i=cur[x];i<G[x].size();i++){
            Edge &e = edges[G[x][i]];
            if (d[x]+1 == d[e.to] && (f=DFS(e.to,min(a,e.cap-e.flow)))>0){
                e.flow+=f;
                edges[G[x][i]^1].flow-=f;
                flow+=f;
                a-=f;
                if (a==0)
                    break;
            }
        }
        return flow;
    }
 
    int Maxflow(int s,int t){
        this->s=s;
        this->t=t;
        int flow = 0;
        while (BFS()){
            memset(cur,0,sizeof(cur));
            flow+=DFS(s,inf);
        }
        return flow;
    }
}dc;
int main(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)scanf("%d",&a[i]);
    int S=0,T=1e5;
    dc.init();
    for(int i=1;i<=An;i++){
        dc.AddEdge(i,T,m*i*i);
    }
    for(int i=1;i<=n;i++){
        for(int j=i;j<=n;j++){
            scanf("%d",&d[i][j]);
            num[i][j]=An+(++cnt);
        }
    }
    for(int i=1;i<=n;i++){
        for(int j=i;j<=n;j++){
            if(i==j){
                d[i][j]-=a[i];
                dc.AddEdge(num[i][i],a[i],inf);
            }
            else{
                dc.AddEdge(num[i][j],num[i][j-1],inf);
                dc.AddEdge(num[i][j],num[i+1][j],inf);
            }
            if(d[i][j]<0){
                dc.AddEdge(num[i][j],T,-d[i][j]);
            }
            else {
                dc.AddEdge(S,num[i][j],d[i][j]);
                ans+=d[i][j];
            }
        }
    }
    printf("%d\n",ans-dc.Maxflow(S,T));
    return 0;
}