Submission #855244

#	Time	Username	Problem	Language	Result	Execution time	Memory
855244		willychan	Chorus (JOI23_chorus)	C++14	61 / 100	840 ms	1372 KiB

chorus

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
//#include<bits/extc++.h>
//__gnu_pbds
const int N = 5005;
pair<ll,int> dp[N];
int Bpa[N];
int n,K;
bool ok(int v){
	for(int i=0;i<=n;i++) dp[i] = {1e18,0};
	dp[0]={0,0};
	for(int i=1;i<=n;i++){
		int cost = 0;
		for(int j=1;j<=i;j++){
			cost+=max(0,i-Bpa[i-j+1]);	
			dp[i] = min({dp[i-j].first+cost+v,dp[i-j].second+1},dp[i]);
		}
	}
	//cout<<(dp[n].second<=K)<<" "<<dp[n].first<<" "<<v<<"\n";
	return (dp[n].second<=K);
}
 
int main(){
	ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	cin>>n>>K;			
	string s;cin>>s;
	int pa = 0;
	int pb = 0;
	for(int i=1;i<=2*n;i++){
		if(s[i-1]=='A') pa++;
		if(s[i-1]=='B') Bpa[++pb]=pa;
	}
	ll l = -1;ll r = 1e9;
	while(r-l>1){
		ll mid = l+((r-l)/2);
		if(ok(mid)) r = mid;
		else l = mid;
	}
	ok(r);
	//cout<<r<<"\n";
	cout<<dp[n].first-r*K<<"\n";
 
	return 0;
}

• Subtask 1: 16 / 16
• Subtask 2: 24 / 24
• Subtask 3: 21 / 21
• Subtask 4: 0 / 26
• Subtask 5: 0 / 13