🛠️ Compare Strings in C with and without strcmp()

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🧑‍💻 Tutorial: Compare Two Strings in C (With & Without strcmp())

In this tutorial, you will learn how to compare two strings entered by the user using:

• ✅ The built-in strcmp() function from <string.h>
• 🛠️ Manual comparison character by character (without using string functions)

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✅ Method 1: Using strcmp() Function

#include <stdio.h>
#include <string.h>

int main() {
    char str1[100], str2[100];

    printf("Enter first string: ");
    fgets(str1, sizeof(str1), stdin);

    printf("Enter second string: ");
    fgets(str2, sizeof(str2), stdin);

    // Remove newline characters if present
    size_t len1 = strlen(str1);
    if (len1 > 0 && str1[len1 - 1] == '\n') {
        str1[len1 - 1] = '\0';
    }

    size_t len2 = strlen(str2);
    if (len2 > 0 && str2[len2 - 1] == '\n') {
        str2[len2 - 1] = '\0';
    }

    // Compare using strcmp()
    if (strcmp(str1, str2) == 0) {
        printf("The strings are equal.\n");
    } else {
        printf("The strings are not equal.\n");
    }

    return 0;
}

📝 Explanation:

• fgets() is used to input strings safely.
• Trailing newline characters are removed.
• strcmp() compares both strings.
• Returns 0 if equal, non-zero otherwise.

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🛠️ Method 2: Without Using strcmp()

#include <stdio.h>

int main() {
    char str1[100], str2[100];
    int i = 0, flag = 0;

    printf("Enter first string: ");
    fgets(str1, sizeof(str1), stdin);

    printf("Enter second string: ");
    fgets(str2, sizeof(str2), stdin);

    // Remove newline characters
    while (str1[i] != '\0') {
        if (str1[i] == '\n') {
            str1[i] = '\0';
            break;
        }
        i++;
    }

    i = 0;
    while (str2[i] != '\0') {
        if (str2[i] == '\n') {
            str2[i] = '\0';
            break;
        }
        i++;
    }

    // Manual comparison
    i = 0;
    while (str1[i] != '\0' && str2[i] != '\0') {
        if (str1[i] != str2[i]) {
            flag = 1;
            break;
        }
        i++;
    }

    if (str1[i] != str2[i]) {
        flag = 1; // Different lengths
    }

    if (flag == 0) {
        printf("The strings are equal.\n");
    } else {
        printf("The strings are not equal.\n");
    }

    return 0;
}

📝 Explanation:

• Both strings are compared character-by-character.
• Newline characters are removed manually.
• Flag is used to track differences.
• This method does not use any string library function.

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📌 Summary

You’ve learned how to compare two strings in C using both strcmp() and manual logic. The built-in function is easier and more reliable, but manual comparison helps build core logic skills.

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