Toggle each character in a string in C

Understanding Character Toggling

Character toggling means converting uppercase letters to lowercase and vice versa.

We will explore three different methods to toggle characters in a string using C.

Method 1: Using a Loop

This method iterates through the string and toggles each character.

#include <stdio.h>
#include <ctype.h>

void toggle_case(char *str) {
    for (int i = 0; str[i] != '\0'; i++) {
        if (islower(str[i]))
            str[i] = toupper(str[i]);
        else if (isupper(str[i]))
            str[i] = tolower(str[i]);
    }
}

int main() {
    char str[100];
    printf("Enter a string: ");
    gets(str);
    toggle_case(str);
    printf("Toggled string: %s\n", str);
    return 0;
}
            

Method 2: Using Recursion

This method toggles characters recursively.

#include <stdio.h>
#include <ctype.h>


void toggle_recursive(char *str, int index) {
    if (str[index] == '\0') return;
    if (islower(str[index]))
        str[index] = toupper(str[index]);
    else if (isupper(str[index]))
        str[index] = tolower(str[index]);
    toggle_recursive(str, index + 1);
}

int main() {
    char str[100];
    printf("Enter a string: ");
    gets(str);
    toggle_recursive(str, 0);
    printf("Toggled string: %s\n", str);
    return 0;
}
            

Method 3: Using Bitwise Operations

This method toggles characters using bitwise XOR operation.

#include <stdio.h>

void toggle_bitwise(char *str) {
    for (int i = 0; str[i] != '\0'; i++) {
        str[i] ^= 32;
    }
}

int main() {
    char str[100];
    printf("Enter a string: ");
    gets(str);
    toggle_bitwise(str);
    printf("Toggled string: %s\n", str);
    return 0;
}