Submission #298118

#	Time	Username	Problem	Language	Result	Execution time	Memory
298118		eriksuenderhauf	Monochrome Points (JOI20_monochrome)	C++17	35 / 100	1685 ms	4236 KiB

monochrome

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 2e5 + 5;
int a[2*N];
ll dp[N];

ll solve(int n, int i) {
  if (dp[i] != 0)
    return dp[i];
  int ptr[2] = {i+n, i+n}, cnt[4] = {0, 0, 0, 0};
  auto next = [&](int& j) {
    j = j+1 < 2*n ? j+1 : j+1-2*n;
  };
  ll val = 0;
  for (int j = i, c = a[i]; j < i+n; c = a[++j]) {
    while (ptr[c] != i && a[ptr[c]] == c)
      cnt[c+2]++, next(ptr[c]);
    next(ptr[c]);
    val += min(cnt[c+2], cnt[c^1]) + cnt[c]++;
  }
  return dp[i] = val;
}

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int get(int l, int r) {
  return uniform_int_distribution<int>(l, r)(rng);
}

int main() {
  ios_base::sync_with_stdio(false); cin.tie(0);
  int n; cin >> n;
  string s; cin >> s;
  for (int i = 0; i < 2*n; i++)
    a[i] = s[i] == 'B';
  ll ans = 0;
  for (int i = 0; i < 500; i++)
    ans = max(ans, solve(n, get(0, n-1)));
  cout << ans << "\n";
}

• Subtask 1: 4 / 4
• Subtask 2: 21 / 21
• Subtask 3: 10 / 10
• Subtask 4: 0 / 65