A wonderful string is defined as a string in which at most one letter occurs an odd number of times.

For example:

• The string “aabbc” is wonderful because only the letter 'c' appears an odd number of times.

• The string “pqpq” is wonderful because all letters appear an even number of times.

• The string “mn” is not wonderful because both 'm' and 'n' appear an odd number of times.

You are given a string word that consists of lowercase English letters from 'a' to 'j'. Your task is to return the total number of wonderful non-empty substringsA substring is any contiguous sequence of characters within the string. in word.

Note: If a substring appears multiple times, each occurrence should be counted separately.

Constraints:

• $1 <=$ word.length $<= 10^3$

• word consists of lowercase English letters from 'a' to 'j'.

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 on how to solve this problem.

Implement your solution in the following coding playground.