[Solution] First Letter to Appear Twice solution leetcode

First Letter to Appear Twice solution leetcode – Given a string s consisting of lowercase English letters, return the first letter to appear twice.

Note:

  • A letter a appears twice before another letter b if the second occurrence of a is before the second occurrence of b.
  • s will contain at least one letter that appears twice.

 

[Solution] First Letter to Appear Twice solution leetcode

Input: s = "abccbaacz"
Output: "c"
Explanation:
The letter 'a' appears on the indexes 0, 5 and 6.
The letter 'b' appears on the indexes 1 and 4.
The letter 'c' appears on the indexes 2, 3 and 7.
The letter 'z' appears on the index 8.
The letter 'c' is the first letter to appear twice, because out of all the letters the index of its second occurrence is the smallest.

First Letter to Appear Twice solution leetcode

Input: s = "abcdd"
Output: "d"
Explanation:
The only letter that appears twice is 'd' so we return 'd'.

 

[Solution] First Letter to Appear Twice solution leetcode

  • 2 <= s.length <= 100
  • s consists of lowercase English letters.
  • s has at least one repeated letter.

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