LeetCode 1796. Second Largest Digit in a String



Given an alphanumeric string s, return the second largest numerical digit that appears in s, or -1 if it does not exist.

An alphanumericstring is a string consisting of lowercase English letters and digits.

Example 1:

Input: s = "dfa12321afd"
Output: 2
Explanation: The digits that appear in s are [1, 2, 3]. The second largest digit is 2.

Example 2:

Input: s = "abc1111"
Output: -1
Explanation: The digits that appear in s are [1]. There is no second largest digit. 


  • 1 <= s.length <= 500
  • s consists of only lowercase English letters and/or digits.


Create a set to store numerical digits and find out the second-largest number.

Python Solution

class Solution:
    def secondHighest(self, s: str) -> int:
        digit_set = set()
        for c in s:
            if c.isdigit():
        if len(digit_set) < 2:
            return -1
        return sorted(list(digit_set))[-2]        
  • Time Complexity: O(Nlog(N)).
  • Space Complexity: O(N).

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