제출 #1135419

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1135419		mychecksedad	Chorus (JOI23_chorus)	C++17	0 / 100	14 ms	31552 KiB

chorus

/* Author : Mychecksdead  */
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define MOD (1000000000+7)
#define MOD1 (998244353)
#define pb push_back
#define all(x) x.begin(), x.end()
#define en cout << '\n'
#define ff first
#define ss second
#define pii pair<int,int>
#define vi vector<int>
const int N = 1e6+100, M = 1e5+10, K = 52, MX = 30;
const double eps = 0.0000001;

struct St{
  double cost = 0;
  int sz = 0;
  int cur_sz = 0;
};

int n, k;
ll A[N], B[N];
string s;
vector<ll> pref(2*N+1), pref2(2*N+1);
pair<double, int> f(double cost){
  vector<array<St, 2>> DP(n+1);
  for(int i = 1; i <= n; ++i){
    int x = i, y = i - 1;
    if(DP[y][0].cost < DP[y][1].cost){
      DP[x][0].cost = DP[y][0].cost + cost + (B[i] < A[i] ? pref[A[i]] - pref[B[i]] : 0ll);
      DP[x][0].sz = DP[y][0].sz + 1;
      DP[x][0].cur_sz = 1;
    
      DP[x][1].cost = DP[y][0].cost + (B[i] < A[i] ? pref[A[i]] - pref[B[i]] : 0ll) + (B[i] < A[i] ? DP[y][0].cur_sz : max(0ll, pref2[A[i]] - (i - DP[y][0].cur_sz)));
      DP[x][1].sz = DP[y][0].sz;
      DP[x][1].cur_sz = DP[y][0].cur_sz + 1;
    }else{
      DP[x][0].cost = DP[y][1].cost + cost + (B[i] < A[i] ? pref[A[i]] - pref[B[i]] : 0ll);
      DP[x][0].sz = DP[y][1].sz + 1;
      DP[x][0].cur_sz = 1;

      DP[x][1].cost = DP[y][1].cost + (B[i] < A[i] ? pref[A[i]] - pref[B[i]] : 0ll) + (B[i] < A[i] ? DP[y][1].cur_sz : max(0ll, pref2[A[i]] - (i - DP[y][0].cur_sz)));
      DP[x][1].sz = DP[y][1].sz;
      DP[x][1].cur_sz = DP[y][1].cur_sz + 1;
    }
    if(i == 1) DP[x][1] = DP[x][0];
    // cout << DP[x][0].cost << ' ' << DP[x][0].sz << " | ";
    // cout << DP[x][1].cost << ' ' << DP[x][1].sz << "\n";
  }
  // en;en;
  return (DP[n][0].cost < DP[n][1].cost ? pair<double, int>{DP[n][0].cost, DP[n][0].sz} : pair<double, int>{DP[n][1].cost, DP[n][1].sz});
}

void solve(){
  cin >> n >> k >> s;
  assert(n != 1);
  assert(k != 1);
  assert(s != "AB");
  int a = 0, b = 0;
  A[0] = 0;
  for(int i = 0; i < 2*n; ++i){
    pref[i + 1] = pref[i];
    pref2[i + 1] = pref2[i];
    if(s[i] == 'A'){
      A[++a] = i+1;
      pref[i + 1]++;
    }else{
      B[++b] = i+1;
      pref2[i + 1]++;
    }
  }
  ll ans = 0;
  double l = 0, r = MOD;
  while(l + eps < r){
    double m = (l+r)/2;
    // cout << m << ":\n";
    auto p = f(m);
    // cout << p.ff << ' ' << p.ss << '\n';
    if(p.ss >= k){
      ans = (ll)(p.ff - p.ss * m);
      l = m;
    }else{
      r = m;
    }
  }
  cout << ans;
}


int main(){
  cin.tie(0); ios::sync_with_stdio(0);
  int tt = 1, aa;
  cout << fixed << setprecision(10);
  // freopen("in.txt", "r", stdin);
  // freopen("out.txt", "w", stdout);
  while(tt--){
    solve();
    en;
  }
  cerr<<"time taken : "<<(float)clock()/CLOCKS_PER_SEC<<" seconds\n";
  return 0;
} 

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