Second Largest Digit in a String
In this problem, we have to find the second largest numerical digit in a given alphanumeric string.
Here’s a stepbystep way to solve this problem:
We initialize a set to hold the unique digits we find in the string. We’ll use a set because it automatically removes duplicates.
We iterate over each character in the string. If the character is a digit, we add it to our set.
After we’ve gone through the entire string, we’ll check the size of our set. If it has less than 2 elements, it means we don’t have a second largest digit, so we return 1.
If our set has at least 2 elements, we sort it in descending order and return the second element (at index 1).


This solution works because it keeps track of all unique digits in the string and returns the second largest one. If no second largest digit exists, it correctly returns 1. The time complexity of this solution is O(n), where n is the length of the string, because we make a single pass through the string. The space complexity is O(1), because the set of digits can contain at most 10 elements.