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Grokking the Coding Interview Patterns in Python

First Unique Character in a String

Explore methods to find the first unique character in a string by mastering data tracking techniques. Learn to solve typical string problems including permutations and anagrams, enhancing your problem-solving skills for coding interviews.

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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:

  • 1≤1 \leq s.length ≤103\leq 10^{3}
  • Only lowercase English letters are accepted.
  • There are no spaces in the string.

Examples

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Understand the problem

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:

First Unique Character in a String

1.

What is the correct answer if the following string is given as input?

s = “awsjawuh”

A.

2

B.

4

C.

3

D.

6

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Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
1
2
3
4
5

Try it yourself

Implement your solution in the following coding playground.

Python
usercode > main.py
def first_unique_char(s):



    # Replace this placeholder return statement with your code

    return -1
First Unique Character in a String