Character Frequency Counting in DSA C - Build from Scratch

Character Frequency Counting

📖 Scenario: Imagine you are analyzing a short message to find out how many times each letter appears. This is useful in text analysis, cryptography, or just understanding letter usage.

🎯 Goal: You will write a program that counts how many times each character appears in a given string.

📋 What You'll Learn

Create a string variable with a fixed message

Create an array to count frequency of each ASCII character

Use a loop to count characters in the string

Print the frequency of each character that appears at least once

💡 Why This Matters

🌍 Real World

Counting character frequency helps in text analysis, such as finding the most common letters in a message or preparing data for compression.

💼 Career

Understanding how to count and analyze characters is useful in software development fields like data processing, cryptography, and natural language processing.

1

Create the message string

Create a character array called message and initialize it with the exact string "hello world".

DSA C

# Your code here

Hint

Use double quotes to create the string inside the array.

2

Create frequency array

Add an integer array called freq of size 256 and initialize all elements to 0.

DSA C

#include 

char message[] = "hello world";

// Your code here

Hint

Use curly braces with 0 to initialize all elements to zero.

3

Count characters in the message

Write a for loop using an integer variable i to iterate over message until the null character '\0' is reached. Inside the loop, increase freq[(unsigned char)message[i]] by 1.

DSA C

#include 

char message[] = "hello world";

int freq[256] = {0};

// Your code here

Hint

Use a loop that stops when you find the '\0' character which marks the end of the string.

4

Print character frequencies

Write a for loop using an integer variable ch from 0 to 255. Inside the loop, if freq[ch] is greater than 0, print the character and its frequency using printf in the format: Character '%c' appears %d times\n.

DSA C

#include 

char message[] = "hello world";

int freq[256] = {0};

int i;
for (i = 0; message[i] != '\0'; i++) {
    freq[(unsigned char)message[i]]++;
}

// Your code here

Hint

Print only characters that appear at least once. Use a loop from 0 to 255 to check all possible characters.