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C Program to Compare Two Strings Using Pointers

Last Updated : 28 Nov, 2024
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In C, two strings are generally compared character by character in lexicographical order (alphabetical order). In this article, we will learn how to compare two strings using pointers.

To compare two strings using pointers, increment the pointers to traverse through each character of the strings while comparing each character at corresponding position. If both strings are completely traversed without finding any mismatch, then they are considered equal. Otherwise, they are unequal.

C 
#include <stdio.h>

int strCmp(char *s1, char *s2) {
  
    // Traverse both strings until a mismatch
  	// is found or one of the string ends
    while (*s1 && (*s1 == *s2)) {
      
        // Move to the next character in str1
        s1++;  
        s2++;
    }

    // If both are equal, this will return 0
    return (*s1 - *s2);
}

int main() {
    char s1[] = "GeeksforGeeks";
    char s2[] = "Geeks";

    int res = strCmp(s1, s2);

    if (res < 0) {
        printf("\"%s\" is lexicographically smaller than \"%s\".\n", s1, s2);
    } else if (res > 0) {
        printf("\"%s\" is lexicographically greater than \"%s\".\n", s1, s2);
    } else {
        printf("\"%s\" is lexicographically equal to \"%s\".\n", s1, s2);
    }

    return 0;
}

Output
"GeeksforGeeks" is lexicographically greater than "Geeks".

Explanation: This method uses pointer dereferencing to compare characters in the strings using equality operator. The pointer is incremented to iterate through the strings until the end of one string is reached.


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