2083. Substrings That Begin and End With the Same Letter π
Description
You are given a 0-indexed string s
consisting of only lowercase English letters. Return the number of substrings in s
that begin and end with the same character.
A substring is a contiguous non-empty sequence of characters within a string.
Example 1:
Input: s = "abcba" Output: 7 Explanation: The substrings of length 1 that start and end with the same letter are: "a", "b", "c", "b", and "a". The substring of length 3 that starts and ends with the same letter is: "bcb". The substring of length 5 that starts and ends with the same letter is: "abcba".
Example 2:
Input: s = "abacad" Output: 9 Explanation: The substrings of length 1 that start and end with the same letter are: "a", "b", "a", "c", "a", and "d". The substrings of length 3 that start and end with the same letter are: "aba" and "aca". The substring of length 5 that starts and ends with the same letter is: "abaca".
Example 3:
Input: s = "a" Output: 1 Explanation: The substring of length 1 that starts and ends with the same letter is: "a".
Constraints:
1 <= s.length <= 105
s
consists only of lowercase English letters.
Solutions
Solution 1
1 2 3 4 5 6 7 8 |
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1 2 3 4 5 6 7 8 9 10 11 12 |
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1 2 3 4 5 6 7 8 9 10 11 |
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1 2 3 4 5 6 7 8 9 |
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