Submission #379486

#	Time	Username	Problem	Language	Result	Execution time	Memory
379486		qwerty234	Monochrome Points (JOI20_monochrome)	C++14	0 / 100	1 ms	492 KiB

monochrome

#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define fi first
#define se second
#define int long long

using namespace std;

const int MAXN = 1e6 + 10;

int n, blue[MAXN], red[MAXN], l1_blue[MAXN], r1_blue[MAXN], l2_blue[MAXN], r2_blue[MAXN];
int l1_red[MAXN], r1_red[MAXN], l2_red[MAXN], r2_red[MAXN];
int closest_left_red[MAXN], closest_left_blue[MAXN];
ll ans[MAXN];
char a[MAXN];

void precalc() {
  for (int i = 1; i <= n; i++) {
    blue[i + n] = blue[i] + 2 * n;
    red[i + n] = red[i] + 2 * n;
  }
  int lastred = 0, lastblue = 0;
  for (int i = 1; i <= 4 * n; i++) {
    int cur = i; if (i > 2 * n) cur -= 2 * n;
    if (a[cur] == 'B') lastblue++; else lastred++;
    closest_left_red[i] = lastred;
    closest_left_blue[i] = lastblue;
  }
  for (int i = 1; i <= n; i++) {
    l1_blue[i] = closest_left_red[blue[i]] + 1;
    r1_blue[i] = closest_left_red[(blue[i] + blue[i + n]) / 2];
    l2_blue[i] = r1_blue[i] + 1;
    r2_blue[i] = closest_left_red[blue[i + n]];

    l1_red[i] = closest_left_blue[red[i]] + 1;
    r1_red[i] = closest_left_blue[(red[i] + red[i + n]) / 2 - 1];
    l2_red[i] = r1_red[i] + 1;
    r2_red[i] = closest_left_blue[red[i + n]];
  }
}

void add(int l, int r, int x) {
  if (l > r)
    return;
  l = (l + 2 * n) % n;
  r = (r + 2 * n) % n;
  if (l <= r) {
    ans[l] += x;
    ans[r + 1] -= x;
  } else {
    ans[l] += x;
    ans[1] += x;
    ans[r + 1] -= x;
  }
}

main() {
//  freopen("input.txt", "r", stdin);
  cin >> n; int b = 0, r = 0;
  for (int i = 1; i <= 2 * n; i++) {
    cin >> a[i];
    if (a[i] == 'B') {
      blue[++b] = i;
    } else {
      red[++r] = i;
    }
  }
  precalc();
  for (int i = 1; i <= n; i++) {
    if (l1_blue[i] <= r1_blue[i]) {
      add(l1_blue[i] - i, r1_blue[i] - i, -blue[i]);
    }
    if (l2_blue[i] <= r2_blue[i]) {
      add(l2_blue[i] - i, r2_blue[i] - i, blue[i + n]);
    }

    if (l1_red[i] <= r1_red[i]) {
      add(i - min(n, r1_red[i]), i - l1_red[i], -red[i + n]);
      add(i - r1_red[i], i - max(n + 1, l1_red[i]), -red[i]);
    }
    if (l2_red[i] <= r2_red[i]) {
      add(i - min(n, r2_red[i]), i - l2_red[i], red[i + n]);
      add(i - r2_red[i], i - max(n + 1, l2_red[i]), red[i]);
    }
  }
  ans[0] -= n;
  ll anss = 0, cur = 0;
  for (int i = 0; i < n; i++) {
    cur += ans[i];
    anss = max(anss, cur / 2);
  }
  cout << anss;
}

Compilation message (stderr)

monochrome.cpp:58:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   58 | main() {
      |      ^

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