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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5.     ios::sync_with_stdio(false);
  6.     cin.tie(nullptr);
  7.  
  8.     int test_cases;
  9.     if (!(cin >> test_cases)) return 0;
  10.     while (test_cases--) {
  11.         int length;
  12.         string input_string;
  13.         cin >> length >> input_string;
  14.  
  15.         char dominant_char = input_string[0];
  16.         int dominant_count = 0;
  17.         for (char ch : input_string) {
  18.             if (ch == dominant_char) {
  19.                 dominant_count++;
  20.             }
  21.         }
  22.         int other_count = length - dominant_count;
  23.         int balance_target = dominant_count - other_count;
  24.  
  25.         if (balance_target == 0) {
  26.             cout << 0 << '\n';
  27.             continue;
  28.         }
  29.  
  30.         vector<int> prefix_balance(length + 1, 0);
  31.         for (int j = 0; j < length; ++j) {
  32.             prefix_balance[j + 1] = prefix_balance[j] + (input_string[j] == dominant_char ? 1 : -1);
  33.         }
  34.  
  35.         unordered_map<int, int> last_seen_balance;
  36.         int min_removal = length + 1;
  37.  
  38.         for (int j = 0; j <= length; ++j) {
  39.             int required_balance = prefix_balance[j] - balance_target;
  40.             auto finder = last_seen_balance.find(required_balance);
  41.             if (finder != last_seen_balance.end()) {
  42.                 min_removal = min(min_removal, j - finder->second);
  43.             }
  44.             last_seen_balance[prefix_balance[j]] = j;
  45.         }
  46.  
  47.         if (min_removal > length) {
  48.             cout << -1 << '\n';
  49.         } else {
  50.             cout << min_removal << '\n';
  51.         }
  52.     }
  53.  
  54.     return 0;
  55. }
Success #stdin #stdout 0.01s 5288KB
comments (?)
stdin 
5
5
bbbab
6
bbaaba
4
aaaa
12
aabbaaabbaab
5
aabaa
stdout 
3
0
4
2
5
https://ideone.com/AM4qp0
language:
C++ (gcc 8.3)
created:
10 days ago
visibility:
public

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