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3412. Find Mirror Score of a String 👍

  • Time: $O(n)$
  • Space: $O(n)$
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class Solution {
 public:
  long long calculateScore(string s) {
    long ans = 0;
    vector<stack<int>> indices(26);

    for (int i = 0; i < s.length(); ++i) {
      const int index = s[i] - 'a';
      const int oppositeIndex = 25 - index;
      if (!indices[oppositeIndex].empty())
        ans += i - indices[oppositeIndex].top(), indices[oppositeIndex].pop();
      else
        indices[index].push(i);
    }

    return ans;
  }
};

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class Solution {
  public long calculateScore(String s) {
    long ans = 0;
    Deque<Integer>[] indices = new ArrayDeque[26];

    for (int i = 0; i < 26; ++i)
      indices[i] = new ArrayDeque<>();

    for (int i = 0; i < s.length(); ++i) {
      final int index = s.charAt(i) - 'a';
      final int oppositeIndex = 25 - index;
      if (!indices[oppositeIndex].isEmpty())
        ans += i - indices[oppositeIndex].poll();
      else
        indices[index].push(i);
    }

    return ans;
  }
}

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class Solution:
  def calculateScore(self, s: str) -> int:
    ans = 0
    indices = [[] for _ in range(26)]

    for i, c in enumerate(s):
      index = ord(c) - ord('a')
      oppositeIndex = 25 - index
      if indices[oppositeIndex]:
        ans += i - indices[oppositeIndex].pop()
      else:
        indices[index].append(i)

    return ans