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2423. Remove Letter To Equalize Frequency 👎

  • Time: $O(26n) = O(n)$
  • Space: $O(26) = O(1)$
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class Solution {
 public:
  bool equalFrequency(string word) {
    vector<int> count(26);

    for (const char c : word)
      ++count[c - 'a'];

    // Try to remove each letter, then check if the frequency of all letters in
    // word are equal
    for (const char c : word) {
      --count[c - 'a'];
      if (equalCount(count))
        return true;
      ++count[c - 'a'];
    }

    return false;
  }

 private:
  bool equalCount(const vector<int>& count) {
    int freq = -1;
    for (const int c : count) {
      if (c == 0 || c == freq)
        continue;
      if (freq == -1)
        freq = c;
      else
        return false;
    }
    return true;
  }
};

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class Solution {
  public boolean equalFrequency(String word) {
    int[] count = new int[26];

    for (final char c : word.toCharArray())
      ++count[c - 'a'];

    // Try to remove each letter, then check if the frequency of all letters in
    // word are equal
    for (final char c : word.toCharArray()) {
      --count[c - 'a'];
      if (equalCount(count))
        return true;
      ++count[c - 'a'];
    }

    return false;
  }

  private boolean equalCount(int[] count) {
    int freq = -1;
    for (final int c : count) {
      if (c == 0 || c == freq)
        continue;
      if (freq == -1)
        freq = c;
      else
        return false;
    }
    return true;
  }
}

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class Solution:
  def equalFrequency(self, word: str) -> bool:
    count = collections.Counter(word)

    # Try to remove each letter, then check if the frequency of all letters in
    # word are equal
    for c in word:
      count[c] -= 1
      if self._equalCount(count):
        return True
      count[c] += 1

    return False

  def _equalCount(self, count: Dict[int, int]) -> bool:
    freq = -1
    for c in count.values():
      if c == 0 or c == freq:
        continue
      if freq == -1:
        freq = c
      else:
        return False
    return True