3438. Find Valid Pair of Adjacent Digits in String

You are given a string s consisting only of digits. A valid pair is defined as two adjacent digits in s such that: - The first digit is not equal to the second. - Each digit in the pair appears in s exactly as many times as its numeric value. Return the first valid pair found in the string s when traversing from left to right. If no valid pair exists, return an empty string. Example 1: Inpu