Submission #1022983

#	Time	Username	Problem	Language	Result	Execution time	Memory
1022983		snpmrnhlol	Group Photo (JOI21_ho_t3)	C++17	100 / 100	457 ms	856 KiB

Main

#include<bits/stdc++.h>
using namespace std;
const int N = 5e3;
const int inf = 2e9;
int v[N],pos[N];
int dp[N];
int fen[N][3];
int n;
void add(int pos,int x,int id){
    for(int i = pos;i < n;i|=(i + 1)){
        fen[i][id]+=x;
    }
}
int get(int pos,int id){
    int r = 0;
    for(int i = pos;i >= 0;i&=(i + 1),i--){
        r+=fen[i][id];
    }
    return r;
}
int main(){
    cin>>n;
    for(int i = 0;i < n;i++){
        cin>>v[i];
        v[i]--;
        pos[v[i]] = i;
        dp[i] = inf;
    }
    int sum2 = 0;
    for(int i = n - 1;i >= 0;i--){
        sum2+=get(n - 1 - pos[i],0);
        dp[i] = min(dp[i],sum2);
        //cout<<sum2<<' ';
        add(n - 1 - pos[i],1,0);
        add(pos[i],1,2);
        int sum = 0;
        for(int j = i - 1;j >= 0;j--){
            sum+=get(pos[j],2);
            sum+=get(n - 1 - pos[j],1);
            add(n - 1 - pos[j],1,1);
            //cout<<j<<' '<<i<<' '<<sum<<'\n';
            dp[j] = min(dp[j], dp[i] + sum);
        }
        for(int j = i - 1;j >= 0;j--){
            add(n - 1 - pos[j],-1,1);
        }
        //cout<<dp[i]<<'\n';
    }
    cout<<dp[0];
    return 0;
}

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 32 / 32
• Subtask 4: 20 / 20
• Subtask 5: 36 / 36