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1624. Largest Substring Between Two Equal Characters 👍

  • Time: $O(n)$
  • Space: $O(1)$
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class Solution {
 public:
  int maxLengthBetweenEqualCharacters(string s) {
    int ans = -1;
    vector<int> lastSeen(26, -1);

    for (int i = 0; i < s.length(); ++i) {
      const int c = s[i] - 'a';
      if (lastSeen[c] == -1)
        lastSeen[c] = i;
      else
        ans = max(ans, i - lastSeen[c] - 1);
    }

    return ans;
  }
};

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class Solution {
  public int maxLengthBetweenEqualCharacters(String s) {
    int ans = -1;
    int[] lastSeen = new int[26];
    Arrays.fill(lastSeen, -1);

    for (int i = 0; i < s.length(); ++i) {
      final int c = s.charAt(i) - 'a';
      if (lastSeen[c] == -1)
        lastSeen[c] = i;
      else
        ans = Math.max(ans, i - lastSeen[c] - 1);
    }

    return ans;
  }
}

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class Solution:
  def maxLengthBetweenEqualCharacters(self, s: str) -> int:
    ans = -1
    lastSeen = {}

    for i, c in enumerate(s):
      if c not in lastSeen:
        lastSeen[c] = i
      else:
        ans = max(ans, i - lastSeen[c] - 1)

    return ans