1796. Second Largest Digit in a String-字符串中第二大的数字

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

An alphanumeric string 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.

Constraints:

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

Solution in python:

class Solution:
    def secondHighest(self, s: str) -> int:
        aset = set()
        for ch in s:
            aset.add(ch)
        for i in range(9, -1, -1):
            if str(i) in aset:
                for j in range(i-1, -1, -1):
                    if str(j) in aset:
                        return j
        return -1