Submission #942035

#	Time	Username	Problem	Language	Result	Execution time	Memory
942035		pcc	Group Photo (JOI21_ho_t3)	C++14	100 / 100	894 ms	77752 KiB

Main

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

#define ll long long
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fs first
#define sc second
#define tlll tuple<ll,ll,ll>


const int mxn = 5050;
int N;
int arr[mxn],pos[mxn];
int aux[mxn][mxn];
ll bit1[mxn],bit2[mxn];
int dp[mxn];

void modify(ll bit[],int p,int v){
	for(;p<mxn;p+=p&-p)bit[p] += v;
	return;
}
int getval(ll bit[],int s,int e){
	int re = 0;
	for(;e>0;e-= e&-e)re += bit[e];
	s--;
	for(;s>0;s-= s&-s)re -= bit[s];
	return re;
}

void calc(){
	fill(dp,dp+mxn,mxn*mxn);
	dp[0] = 0;
	for(int i = 0;i<=N;i++){
		memset(bit1,0,sizeof(bit1));
		memset(bit2,0,sizeof(bit2));
		int sh = 0;
		for(int j = 1;j<=N;j++){
			if(j>i)modify(bit1,pos[j],1);
		}
		for(int j = i+1;j<=N;j++){
			int tdp = dp[i]+aux[i+1][j];
			sh = sh+getval(bit1,0,pos[j]-1)-getval(bit2,pos[j]+1,N);
			modify(bit1,pos[j],-1);
			modify(bit2,pos[j],1);
			dp[j] = min(dp[j],tdp+sh);
			//cerr<<i<<' '<<j<<' '<<tdp<<":"<<sh<<endl;
		}
	}
	//for(int i = 1;i<=N;i++)cerr<<dp[i]<<' ';cerr<<endl;
	return;
}

int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin>>N;
	for(int i = 1;i<=N;i++)cin>>arr[i],pos[arr[i]] = i;
	for(int s = 1;s<=N;s++){
		memset(bit1,0,sizeof(bit1));
		for(int e = s;e<=N;e++){
			aux[s][e] = aux[s][e-1];
			aux[s][e] += getval(bit1,0,pos[e]);
			modify(bit1,pos[e],1);
		}
	}
	calc();
	cout<<dp[N];
}

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