w3resource

C Programming: Compare two strings without using string library functions

C String: Exercise-6 with Solution

Write a program in C to compare two strings without using string library functions.

Sample Solution:

C Code:

 // C program to compare the two strings without using strcmp() function
#include <stdio.h>
#define str_size 100 // Declare the maximum size of the string

// Function to compare two strings
int test(char* s1, char* s2) {
    int flag = 0; // Initialize a flag variable to indicate string equality or inequality

    // Loop to compare characters in the strings until null terminator '\0' is found in both strings
    while (*s1 != '\0' || *s2 != '\0') {
        if (*s1 == *s2) { // Check if the characters in both strings are equal
            s1++; // Move to the next character in the first string
            s2++; // Move to the next character in the second string
        } else if ((*s1 == '\0' && *s2 != '\0') || (*s1 != '\0' && *s2 == '\0') || *s1 != *s2) {
            // Check for cases where one string ends before the other or characters at the same index are not equal
            flag = 1; // Set the flag to indicate inequality
            break; // Exit the loop as inequality is found
        }
    }
    return flag; // Return the flag indicating string equality (0) or inequality (1)
}

// Main function
int main(void) {
    char str1[str_size], str2[str_size]; // Declare character arrays for the two strings
    int flg = 0; // Initialize a flag variable

    printf("\nInput the 1st string : ");
    fgets(str1, sizeof str1, stdin); // Read the first string from the standard input (keyboard)
    printf("Input the 2nd string : ");
    fgets(str2, sizeof str2, stdin); // Read the second string from the standard input (keyboard)

    printf("\nString1: %s", str1); // Display the first string
    printf("String2: %s", str2); // Display the second string

    flg = test(str1, str2); // Call the function to compare the strings

    // Display the comparison result based on the flag value
    if (flg == 0) {
        printf("\nStrings are equal.\n");
    } else if (flg == 1) {
        printf("\nStrings are not equal.");
    }

    return 0; // Return 0 to indicate successful program execution
}

Sample Output:


Check the length of two strings:
--------------------------------
Input the 1st string : aabbcc
Input the 2nd string : abcdef

String1: aabbcc
String2: abcdef

Strings are not equal.

Sample Output:

Check the length of two strings:
--------------------------------
Input the 1st string : aabbcc
Input the 2nd string : aabbcc

String1: aabbcc
String2: aabbcc

Strings are equal.

Flowchart:

Flowchart: Compare two strings without using string library functions

C Programming Code Editor:

Improve this sample solution and post your code through Disqus.

Previous: Write a program in C to count the total number of words in a string.
Next: Write a program in C to count total number of alphabets, digits and special characters in a string.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



Become a Patron!

Follow us on Facebook and Twitter for latest update.

It will be nice if you may share this link in any developer community or anywhere else, from where other developers may find this content. Thanks.

https://w3resource.com/c-programming-exercises/string/c-string-exercise-6.php