Given a string s, return the length of the longest substring between two equal characters, excluding the two characters. If there is no such substring return -1.
A substring is a contiguous sequence of characters within a string.
Example 1:
Input: s = "aa"
Output: 0
Explanation: The optimal substring here is an empty substring between the two 'a's.
Example 2:
Input: s = "abca" Output: 2 Explanation: The optimal substring here is "bc".
Example 3:
Input: s = "cbzxy" Output: -1 Explanation: There are no characters that appear twice in s.
Example 4:
Input: s = "cabbac" Output: 4 Explanation: The optimal substring here is "abba". Other non-optimal substrings include "bb" and "".
Constraints:
1 <= s.length <= 300scontains only lowercase English letters.
Solution: Hashtable
Remember the first position each letter occurs.
Time complexity: O(n)
Space complexity: O(26)
C++
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class Solution { public: int maxLengthBetweenEqualCharacters(string s) { vector<int> first(26, -1); int ans = -1; for (int i = 0; i < s.length(); ++i) { int& p = first[s[i] - 'a']; if (p != -1) { ans = max(ans, i - p - 1); } else { p = i; } } return ans; } }; |
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