Compare Two Strings

Introduction:

This C program is designed to compare two strings inputted by the user. It checks for equality and determines the lexicographical order of the strings. The program uses a custom function to perform the comparison, illustrating basic string manipulation techniques in C. This functionality is important in many applications, such as sorting, searching, and validating user inputs.

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

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

    printf("Enter the first string: ");
    fgets(str1, sizeof(str1), stdin);
    str1[strcspn(str1, "\n")] = 0; // Remove newline character

    printf("Enter the second string: ");
    fgets(str2, sizeof(str2), stdin);
    str2[strcspn(str2, "\n")] = 0; // Remove newline character

    int cmpResult = strcmp(str1, str2);
    if (cmpResult == 0) {
        printf("The two strings are equal.\n");
    } else if (cmpResult < 0) {
        printf("The first string is less than the second string.\n");
    } else {
        printf("The first string is greater than the second string.\n");
    }

    return 0;
}

Include Header Files:

• #include <stdio.h>: This header file is included for standard input and output functions like printf and fgets.
• #include <string.h>: This header file is included for string manipulation functions like strcmp.

Declare String Arrays:

• char str1[100], str2[100];: Two character arrays are declared to hold the input strings.

Input the First String:

• printf("Enter the first string: ");: Prompts the user for input.
• fgets(str1, sizeof(str1), stdin);: Reads a line of text, including spaces, and stores it in str1.
• str1[strcspn(str1, "\n")] = 0;: This line removes the newline character that fgets adds to the string. strcspn finds the length of the string until the newline character, and it is replaced with a null terminator.

Input the Second String:

• Similar to the first string, the program prompts for and reads the second string, storing it in str2 and removing any newline character.

Compare the Strings:

• int cmpResult = strcmp(str1, str2);: The strcmp function compares the two strings:
  • It returns 0 if the strings are equal.
  • It returns a negative value if str1 is less than str2 (lexicographically).
  • It returns a positive value if str1 is greater than str2.

Output the Result of the Comparison:

• The program checks the value of cmpResult:
  • If it is 0, it prints that the two strings are equal.
  • If it is less than 0, it prints that the first string is less than the second.
  • If it is greater than 0, it prints that the first string is greater than the second.

Return Statement:

• return 0;: Indicates successful completion of the program.

Input/Output Block:

Input:

• The user is prompted to enter two strings for comparison.

Example Input:

Enter the first string: Hello
Enter the second string: Hello, World!

Output:

• The program indicates whether the strings are equal or which one is lexicographically greater.

Example Output:

The first string is less than the second string.

Conclusion:

The string comparison program effectively demonstrates how to compare two strings in C using custom logic. By iterating through the characters of both strings, the program determines their equality and relative order in a clear and efficient manner. This capability is essential in various programming scenarios, including data validation, user input handling, and sorting algorithms. Overall, the program serves as a practical example of string manipulation and comparison techniques, reinforcing fundamental programming concepts in C.