Grokking the Coding Interview Patterns in C#/

...

/

Solution: First Unique Character in a String

Solution: First Unique Character in a String

Let's solve the First Unique Character in a String problem using the Knowing What to Track pattern.

We'll cover the following...

Statement

For a given string of characters, s, your task is to find the first non-repeating character and return its index. Return −1-1 if there’s no unique character in the given string.

Constraints:

  • Only lowercase english letters are accepted.
  • There are no spaces in the string.

Solution

We need to keep track of the number of occurrences of each character in the string. To achieve this, we can use a hash map to store the character as a key and its number of occurrences in the string as its corresponding value.

The algorithm proceeds through the following steps:

  • Create a hash map and start a loop to traverse over the given input string. ...