Submission #936571

#	Time	Username	Problem	Language	Result	Execution time	Memory
936571		abcdehello	Group Photo (JOI21_ho_t3)	C++17	100 / 100	2886 ms	99924 KiB

Main

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
int n,a[5050],dp[5050],cnt[5050][5050],ind[5050];//cnt[i][j]=count of a[x] (x<i) s.t. a[x]>=j
ordered_set st;
int count(int l,int r){
	return (cnt[r][n]-cnt[r][r])-(cnt[l-1][n]-cnt[l-1][r]);
}
int main(){
	cin >> n;
	for (int i=1;i<=n;i++) cin >> a[i],ind[a[i]]=i;
	//for (int i=1;i<=n;i++) ind[i]+=ind[i-1];
	for (int i=1;i<=n;i++){
		for (int j=1;j<i;j++){
			cnt[a[i]][a[j]]++,cnt[a[i]][n+1]--;
		}
		for (int j=1;j<=n+1;j++) cnt[a[i]][j]+=cnt[a[i]][j-1];
	}

	for (int i=1;i<=n;i++){
		for (int j=1;j<=n;j++) cnt[i][j]+=cnt[i-1][j];
	}
	dp[0]=0;
	ind[0]=INT_MAX;
	for (int i=1;i<=n;i++){
		dp[i]=INT_MAX;
		int cnt=0;
		st.clear();
		st.insert(ind[i]);
		for (int j=i-1;j>=0;j--){
			dp[i]=min(dp[i],dp[j]+count(j+1,i)+cnt);
			cnt+=st.size()-st.order_of_key(ind[j]);
			st.insert(ind[j]);
		}
	}
	cout << dp[n] << "\n";
}

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