Length of the string without using strlen() function in C

Understanding String Length Calculation

In C, the strlen() function is commonly used to determine the length of a string. However, we can find the length without using it by iterating through the string manually.

We will explore three different methods to find the length of a string in C.

Method 1: Using a Loop

This method iterates through the string character by character to count the length.

#include <stdio.h>

int string_length(char str[]) {
    int count = 0;
    while (str[count] != '\0') {
        count++;
    }
    return count;
}

int main() {
    char str[100];
    printf("Enter a string: ");
    gets(str);
    printf("Length of the string is: %d", string_length(str));
    return 0;
}
            

Method 2: Using Recursion

This method finds the length of a string by calling a function recursively.

#include <stdio.h>

int string_length_recursive(char str[], int index) {
    if (str[index] == '\0')
        return 0;
    return 1 + string_length_recursive(str, index + 1);
}

int main() {
    char str[100];
    printf("Enter a string: ");
    gets(str);
    printf("Length of the string is: %d", string_length_recursive(str, 0));
    return 0;
}
            

Method 3: Using Pointers

This method finds the length of a string using pointer arithmetic.

#include <stdio.h>

int string_length_pointer(char *str) {
    char *ptr = str;
    while (*ptr != '\0') {
        ptr++;
    }
    return ptr - str;
}

int main() {
    char str[100];
    printf("Enter a string: ");
    gets(str);
    printf("Length of the string is: %d", string_length_pointer(str));
    return 0;
}