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Grokking the Coding Interview Patterns

Number of Wonderful Substrings

Understand how to identify and count wonderful substrings where at most one letter appears an odd number of times. Explore hash map techniques to solve this problem and enhance your ability to apply coding patterns in interviews.

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Statement

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 ...