First Non Repeating Character Using Hash in DSA Python - Build from Scratch

First Non Repeating Character Using Hash

📖 Scenario: Imagine you are building a simple text analyzer tool. One of the features is to find the first character in a sentence that does not repeat. This helps highlight unique characters for fun word games or puzzles.

🎯 Goal: Build a program that finds the first non-repeating character in a given string using a hash (dictionary) to count character occurrences.

📋 What You'll Learn

Create a string variable with a specific sentence

Create a dictionary to count characters

Use a loop to fill the dictionary with character counts

Use another loop to find the first character with count 1

Print the first non-repeating character or a message if none found

💡 Why This Matters

🌍 Real World

Finding unique characters is useful in text analysis, cryptography, and word games.

💼 Career

Understanding how to count and analyze data using dictionaries is a key skill in programming and data processing jobs.

1

Create the input string

Create a string variable called text and set it to the exact value 'swiss'.

DSA Python

# Create the string variable 'text' with value 'swiss'
# Your code here

Hint

Use single quotes around the word swiss.

2

Create a dictionary to count characters

Create an empty dictionary called char_count to store character counts.

DSA Python

text = 'swiss'
# Create an empty dictionary called 'char_count'
# Your code here

Hint

Use curly braces {} to create an empty dictionary.

3

Count characters using a loop

Use a for loop with variable char to iterate over text. Inside the loop, update char_count[char] to count how many times each character appears.

DSA Python

text = 'swiss'
char_count = {}
# Use a for loop to count characters in 'text'
# Your code here

Hint

Check if char is already a key in char_count. If yes, add 1; if no, set to 1.

4

Find and print the first non-repeating character

Use a for loop with variable char to iterate over text. Inside the loop, check if char_count[char] is 1. If yes, print char and break the loop. If no such character is found, print 'No non-repeating character found'.

DSA Python

text = 'swiss'
char_count = {}
for char in text:
    if char in char_count:
        char_count[char] += 1
    else:
        char_count[char] = 1

# Find and print the first non-repeating character
# Your code here

Hint

Use a for-else structure to print the character or a message if none found.