C Program to Compare Two Strings.

Comparing two strings is a fundamental operation in programming, allowing us to determine whether two sequences of characters are the same or not. In C, strings are arrays of characters, and comparing them involves comparing each character of the arrays.

There are multiple ways to perform string comparison in C programming and here we are going to learn each of them.

String Comparison Using Loop.

We can manually compare each character of the two strings using a loop. This approach gives you more control and is useful when you need to implement custom comparison logic.

C Code:

// C Program to compare two string using loop
#include <stdio.h>
#include <string.h>

int main() {
    char str1[] = "Apple";
    char str2[] = "Apples";

    int i = 0;
    //comparing two string char by char
    while (str1[i] != '\0' && str2[i] != '\0') {
        if (str1[i] != str2[i]) {
            printf("The strings are not equal.\n");
            return 0;
        }
        i++;
    }

    if (str1[i] == '\0' && str2[i] == '\0') {
        printf("The strings are equal.\n");
    } else {
        printf("The strings are not equal.\n");
    }

    return 0;
}

Output:

The strings are not equal.

Here, we're using a while loop to iterate through the characters of both strings. The loop continues as long as the characters in both strings are not null ('\0'). If at any point we find a character that doesn't match, we conclude that the strings are not equal. If the loop completes successfully without any mismatch and both strings end at the same point, we conclude that the strings are equal.

String Comparison Using strcmp() Function.

In this approach, we're using the strcmp() function from the string.h library. This function compares two strings and returns an integer value indicating their relationship:

If the return value is 0, it means the strings are equal.

If the return value is negative, it means the first string (str1 in our case) is less than the second string (str2).

If the return value is positive, it means the first string is greater than the second string.

C Code:

// C Program to compare two string using strcmp
#include <stdio.h>
#include <string.h>

int main() {
    char str1[] = "Hello";
    char str2[] = "Hello";
    //built-in function to compare string
    int result = strcmp(str1, str2);

    if (result == 0) {
        printf("The strings are equal.\n");
    } else if (result < 0) {
        printf("str1 is less than str2.\n");
    } else {
        printf("str1 is greater than str2.\n");
    }

    return 0;
}

Output:

The strings are equal.

You can use the strcmp() function for a simple comparison, and implement a loop to compare characters manually.

C Program to Compare Two Strings.

String Comparison Using Loop.

String Comparison Using strcmp() Function.

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