Submission #1128323

#	Time	Username	Problem	Language	Result	Execution time	Memory
1128323		jj_master	Group Photo (JOI21_ho_t3)	C++20	100 / 100	549 ms	313268 KiB

Main

// JOI 2021 (Group Photo)
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
#define ins insert
#define eb emplace_back

ll n;
const int mxn = 5001;
ll it[mxn];
ll dp[mxn];
ll ind[mxn];
ll cost[mxn][mxn];
ll pre[mxn][mxn];

void sol()
{
    cin >> n;
	for(ll i=0;i<n;i++){
		cin >> it[i];
		ind[it[i]] = i;
	}
	for(ll i=1;i<=n;i++){
		for(ll j=1;j<=n;j++){
			pre[i][j] = pre[i][j-1];
			if(ind[j] > ind[i]){
				pre[i][j]++;
			}
		}
	}
	for(ll i=1;i<=n;i++){
		for(ll j=i;j<=n;j++){
			cost[i][j] = 0;
			if(i < j){
				cost[i][j] += cost[i][j-1];
			}
			cost[i][j] += pre[j][i-1];
			if(i < j){
				cost[i][j] += (j - i) - (pre[j][j-1] - pre[j][i-1]);
			}
		}
	}
	for(ll i=0;i<=n;i++){
		dp[i]  = 1e9;
	}
	dp[0] = 0;
	for(ll i=1;i<=n;i++){
		for(ll j=1;j<=i;j++){
			dp[i] = min(dp[i], dp[j-1] + cost[j][i]);
		}
	}
	cout << dp[n] << '\n';
}

int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	sol();
	return 0;
}

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