2022/round2/perfectly_balanced_ch1.cpp

#include <iostream>
#include <vector>
using namespace std;

using vi = vector<int>;

bool almost_perfect(const vi &big, const vi &small) {
  int diff = 0;
  for (int c = 0; c < 26; c++) {
    if (big[c] < small[c]) {
      return false;
    }
    diff += big[c] - small[c];
  }
  return diff == 1;
}

int solve() {
  string S;
  cin >> S;
  vector<vi> pre(S.size() + 1, vi(26));
  for (int i = 1; i <= (int)S.size(); i++) {
    pre[i] = pre[i - 1];
    pre[i][S[i - 1] - 'a']++;
  }
  int Q;
  cin >> Q;
  int ans = 0;
  for (int i = 0, l, r; i < Q; i++) {
    cin >> l >> r;
    --l, --r;
    if ((r - l + 1) % 2 == 0) {
      continue;
    }
    auto get_freqs = [&](int l, int r) {
      vi res;
      for (int c = 0; c < 26; c++) {
        res.push_back(pre[r + 1][c] - pre[l][c]);
      }
      return res;
    };
    int m = (l + r) / 2;
    if (almost_perfect(get_freqs(l, m), get_freqs(m + 1, r)) ||
        almost_perfect(get_freqs(m, r), get_freqs(l, m - 1))) {
      ans++;
    }
  }
  return ans;
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int T;
  cin >> T;
  for (int t = 1; t <= T; t++) {
    cout << "Case #" << t << ": " << solve() << endl;
  }
  return 0;
}