Submission #493794

#	Time	Username	Problem	Language	Result	Execution time	Memory
493794		nathanlee726	Group Photo (JOI21_ho_t3)	C++14	100 / 100	420 ms	392496 KiB

Main

#include<bits/stdc++.h>
using namespace std; 
#define ll long long
#define int ll
#define pii pair<int,int>
#define X first
#define Y second
#define F(n) Fi(i,n) 
#define Fi(i,n) Fl(i,0,n)
#define Fl(i,l,n) for(int i=l;i<n;i++)
#define all(x) x.begin(),x.end()
#define sz(x) ((int)x.size())
#define abs(x) ((x)>0?(x):-(x))
#define pb push_back

int n,tab[5005][5005],stab[5005][5005],a[5005],b[5005],dp[5005];

int qry(int l1,int r1,int l2,int r2){
	//cout<<l1<<" "<<r1<<" "<<l2<<" "<<r2<<endl;
	//cout<<stab[r1][r2]<<" "<<stab[r1][l2-1]<<" "<<stab[l1-1][r2]<<" "<<stab[l1-1][l2-1]<<endl;
	return stab[r1][r2]-stab[r1][l2-1]-stab[l1-1][r2]+stab[l1-1][l2-1];
}

signed main(){
	ios_base::sync_with_stdio(0);cin.tie(0);
	cin>>n;
	F(n)cin>>a[i],b[a[i]]=i;
	int s=0;
	memset(tab,0,sizeof(tab));
	F(n)for(int j=i+1;j<n;j++){
		if(b[i+1]<b[j+1])s++,tab[i+1][j+1]=0;
		else tab[i+1][j+1]=1;
	}
	for(int i=0;i<=n;i++)stab[i][0]=stab[0][i]=0;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++)stab[i][j]=tab[i][j]+stab[i-1][j]+stab[i][j-1]-stab[i-1][j-1];
	}
	/*F(n+1){
		Fi(j,n+1)cout<<stab[i][j]<<" ";
		cout<<endl;
	}*/
	dp[n]=s;
	for(int i=n-1;i>=1;i--){
		dp[i]=1e9;
		for(int j=i+1;j<=n;j++){
			int tt=qry(1,i,i+1,j);
			dp[i]=min(dp[i],dp[j]-(i*(j-i))+tt*2);
		}
	}
	/*int no=n;
	for(int i=n-1;i>=1;i--){
		int tt=qry(1,i,i+1,no);
		cout<<tt<<" "<<(i*(no-i))-tt<<endl;
		if(tt<(i*(no-i))-tt){
			s-=((i*(no-i))-tt*2);
			no=i;
		}
		cout<<s<<endl;
	}*/
	s=1e9;
	F(n)s=min(dp[i+1],s);
	cout<<s<<endl;
	return 0;
}
/*

5 4
5 3
5 1
4 3
4 1
3 1
2 1
8 7
*/

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