You are given an integer array nums and an integer x.

A contiguous subarray is considered valid if the sum of its elements satisfies both of the following conditions:

• The most significant digit (first digit) of the sum is equal to x.

• The least significant digit (last digit) of the sum is equal to x.

Return the total number of valid subarrays in nums.

Constraints:

• $1 \leq$ nums.length $\leq 10^5$

• $1 \leq$ nums[i] $\leq 10^9$

• $1 \leq$ x $\leq 9$

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.