Submission #1042471

#	Time	Username	Problem	Language	Result	Execution time	Memory
1042471		abczz	Chorus (JOI23_chorus)	C++17	0 / 100	1 ms	2404 KiB

chorus

#include <iostream>
#include <algorithm>
#include <deque>
#include <vector>
#include <array>
#include <cmath>
#define ll long long
#define ld long double


using namespace std;

ll n, k, l, r, mid, dp[1000000];
ll tot[1000000];
vector <ll> A, B, nxA, ps;
string S, T;

ll C(ll l, ll r) {
  if (nxA[l] > r) return 0;
  ll nx = max(l, nxA[l]), cnt = r-nx+1, cnt2 = max(0LL, l-nxA[l]);
  return ps[r]-(nx ? ps[nx-1] : 0)-cnt*B[l]-cnt*(cnt-1)/2-(r-l+1)*cnt2;
}

void solve() {
  dp[0] = C(0, 0) + mid, tot[0] = 1;
  int j = 0;
  for (int i=1; i<n; ++i) {
    dp[i] = C(0, i) + mid, tot[i] = 1;
    while (j+1 < i) {
      if (dp[j] + C(j+1, i) >= dp[j+1] + C(j+2, i)) ++j;
      else break;
    }
    if (dp[i] >= (j == -1 ? C(j+1, i) : dp[j] + C(j+1, i)) + mid) {
      dp[i] = (j == -1 ? C(j+1, i) : dp[j] + C(j+1, i)) + mid;
      tot[i] = tot[j] + 1;
    }
  }
}


int main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cin >> n >> k >> S;
  for (int i=0; i<2*n; ++i) {
    if (S[i] == 'A') {
      ps.push_back((ps.empty() ? 0 : ps.back()) + i);
      A.push_back(i);
    }
    else {
      B.push_back(i);
      nxA.push_back(A.size());
    }
  }
  l = 0, r = n*n;
  while (l < r) {
    mid = (l+r+1)/2;
    solve();
    if (k > tot[n-1]) r = mid-1;
    else l = mid;
  }
  mid = l;
  solve();
  cout << dp[n-1] - k * mid << '\n';
}

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