Example: Anagram Check (Character Counting Method) in C

// Anagram Check (Character Counting Method)
#include <stdio.h>
#include <string.h>
#include <stdlib.h> // For EXIT_FAILURE and dynamic allocation if needed, not strictly for this version

// Assuming ASCII character set for simplicity (0-255)
#define MAX_CHARS 256

// Function to check if two strings are anagrams using character counting
int areAnagramsCounting(char *str1, char *str2) {
    // Step 1: Declare a frequency array and initialize it to zeros
    int count[MAX_CHARS] = {0};

    // Step 2: Get lengths of both strings
    int len1 = strlen(str1);
    int len2 = strlen(str2);

    // Step 3: If lengths are different, they cannot be anagrams
    if (len1 != len2) {
        return 0; // Not anagrams
    }

    // Step 4: For the first string, increment count for each character
    for (int i = 0; i < len1; i++) {
        count[(unsigned char)str1[i]]++;
    }

    // Step 5: For the second string, decrement count for each character
    for (int i = 0; i < len2; i++) {
        count[(unsigned char)str2[i]]--;
    }

    // Step 6: Check if all counts in the array are zero
    // If any count is non-zero, it means character frequencies don't match
    for (int i = 0; i < MAX_CHARS; i++) {
        if (count[i] != 0) {
            return 0; // Not anagrams
        }
    }

    // Step 7: If all counts are zero, they are anagrams
    return 1;
}

int main() {
    char str1[] = "anagram";
    char str2[] = "nagaram";
    char str3[] = "rat";
    char str4[] = "car";

    printf("Checking \"%s\" and \"%s\":\n", str1, str2);
    if (areAnagramsCounting(str1, str2)) {
        printf("They are anagrams.\n");
    } else {
        printf("They are not anagrams.\n");
    }

    printf("\nChecking \"%s\" and \"%s\":\n", str3, str4);
    if (areAnagramsCounting(str3, str4)) {
        printf("They are anagrams.\n");
    } else {
        printf("They are not anagrams.\n");
    }

    return 0;
}