You are given an integer array nums. Find the maximum sum of a pair of numbers from nums such that the largest digit in both numbers is equal.

Return the maximum sum among all such pairs, or $-1$ if no valid pair exists.

Constraints:

• $2 \leq$ nums.length $\leq 100$

• $1 \leq$ nums[i] $\leq 10^4$

Now, let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.