[Leet Code] Second Largest Digit in a String

Leetcode: https://leetcode.com/problems/second-largest-digit-in-a-string/

Problem:

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.