For example, ball < cat, dog < dorm, Happy < happy, Zoo < ball. A substring of a string is a contiguous block of characters in the string. For example, the substrings of abc are a, b, c, ab, bc, and ...

- So if left substring have alphabet same as right substring , they will cancel each other out and no change is needed - if alphabet in right substring don't exist in left substring , the value will ...