Submission #833771

#	Time	Username	Problem	Language	Result	Execution time	Memory
833771		CSQ31	Chorus (JOI23_chorus)	C++17	0 / 100	1 ms	340 KiB

chorus

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define sz(a) (int)(a.size())
#define all(a) a.begin(),a.end()
#define lb lower_bound
#define ub upper_bound
#define owo ios_base::sync_with_stdio(0);cin.tie(0);
#define debug(...) fprintf(stderr, __VA_ARGS__),fflush(stderr)
#define time__(d) for(long blockTime = 0; (blockTime == 0 ? (blockTime=clock()) != 0 : false);\
debug("%s time : %.4fs\n", d, (double)(clock() - blockTime) / CLOCKS_PER_SEC))
typedef long long int ll;
typedef long double ld;
typedef pair<ll,ll> PII;
typedef pair<int,int> pii;
typedef vector<vector<int>> vii;
typedef vector<vector<ll>> VII;
ll gcd(ll a,ll b){if(!b)return a;else return gcd(b,a%b);}
const int MAXN = 1e6+5;
int a[MAXN],seg[MAXN],n,k;
ll dp[MAXN],p[MAXN];
struct line{
	ll m = 0,c = 0;
	int cnt = 0;
	line(){}
	line(ll _m,ll _c,int _cnt):m(_m),c(_c),cnt(_cnt){}
	ll eval(ll x){return m*x+c;}
};
deque<line>hull;
void add(line t){
	while(sz(hull)>1){
		line a = hull[sz(hull)-2];
		line b = hull[sz(hull)-1];
		//inter(t,a) >=  inter(t,b)
		if((t.c - a.c) * (b.m - t.m) >= (a.m - t.m) * (t.c - b.c))hull.pop_back();
		else break;
	}	
	hull.push_back(t);
}
ll query(ll x){
	while(sz(hull)>1 && hull[1].eval(x) >= hull[0].eval(x)){
		//hull[1].cnt = max(hull[1].cnt,hull[0].cnt);
		hull.pop_front();
	}
	return hull[0].eval(x);
}
int find(ll x){
	hull.clear();
	int l = -1;
	for(int i=1;i<=n;i++){
		while(l+1<i && a[l+1] <= i){
			l++;
			add(line(l,-p[l]-dp[l],seg[l]));
		}
		if(l+1==i && a[i] <= i){
			dp[i] = i*1LL*i - p[i] - query(i) + x;
			seg[i] = seg[hull[0].m]+1;
		}else{
			dp[i] = l*1LL*i - p[l] - query(i) + x;
			seg[i] = seg[hull[0].m]+1;
		}
	}
	/*
	cout<<x<<'\n';
	for(int i=1;i<=n;i++)cout<<dp[i]<<" ";
	cout<<'\n';
	for(int i=1;i<=n;i++)cout<<seg[i]<<" ";
	cout<<'\n';
	* */
	return seg[n];
	
}
int main()
{
	owo
	string s;
	cin>>n>>k>>s;
	int cur = 0,nxt = 0;
	for(int i=0;i<2*n;i++){
		if(s[i] == 'A')cur++;
		else a[++nxt] = cur;
	}
	//for(int i=1;i<=n;i++)cout<<a[i]<<" ";
	//cout<<'\n';
	
	for(int i=1;i<=n;i++)p[i] = p[i-1]+a[i];
	ll l = -100,r = n*1LL*n;
	while(r>=l){
		ll m = (l+r)/2;
		if(find(m)<k)r = m-1;
		else l = m+1;
	}
	find(l);
	cout<<dp[n] - k*1LL*l;
}

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