Example: Character Frequency Counter in C

C
C++
C#
Java
Python
PHP
// Character Frequency Counter
#include <stdio.h>
#include <string.h> // For strlen()

// Define a constant for the number of possible ASCII characters
#define ASCII_SIZE 256

int main() {
    char str[] = "hello world";
    int i = 0;

    // Create an array to store the frequency of each character (our pigeonholes)
    int freq[ASCII_SIZE] = {0}; // Initialize all counts to 0

    printf("Original string: \"%s\"\n", str);

    // Iterate through the string and increment the count for each character
    while (str[i] != '\0') {
        // Use the character's ASCII value as an index (pigeonhole)
        freq[(unsigned char)str[i]]++;
        i++;
    }

    printf("Character frequencies:\n");
    // Print the frequency of characters that appeared
    for (i = 0; i < ASCII_SIZE; i++) {
        if (freq[i] > 0) {
            printf("  '%c' : %d\n", (char)i, freq[i]);
        }
    }

    return 0;
}