Example: Character Frequency - Iterative with Pointers in C

// Character Frequency - Iterative with Pointers
#include <stdio.h>
#include <string.h> // Required for strlen

#define MAX_CHARS 256 // Assuming ASCII characters

void calculateFrequencyIterative(const char *str, int *freq) {
    // Initialize frequency array to all zeros
    for (int i = 0; i < MAX_CHARS; i++) {
        freq[i] = 0;
    }

    // Iterate through the string using a pointer
    const char *ptr = str;
    while (*ptr != '\0') {
        // Increment frequency for the character pointed to by ptr
        // Type casting *ptr to unsigned char ensures it's treated as a positive index
        freq[(unsigned char)*ptr]++;
        ptr++; // Move the pointer to the next character
    }
}

int main() {
    char inputString[] = "Programming is fun.";
    int frequency[MAX_CHARS];

    calculateFrequencyIterative(inputString, frequency);

    printf("Character frequencies for \"%s\":\n", inputString);
    for (int i = 0; i < MAX_CHARS; i++) {
        if (frequency[i] > 0) {
            printf("Character '%c': %d\n", (char)i, frequency[i]);
        }
    }

    return 0;
}