C program to compare two strings using pointers

Learn: How to compare two strings using pointers in C programming language?

Problem statement

Given two strings, we have to write a C program to compare them using the pointers.

Comparing two strings using pointers

Below are the steps to compare two strings using the pointers:

Declare two string variables.
Create two pointers for strings, and initialize them with the string variables.
Now, input and print the two strings.
Now, to compare the strings, use a for loop and compare strings character-wise. If any character (in both strings) is not the same. Then take a flag variable, break the loop, and print the appreciate messages.

Program to compare two strings using pointers in C

#include <stdio.h>

//Macro for maximum number of characters in a string
#define MAX 100

int main()
{
    //declare string variables
    char str1[MAX] = { 0 };
    char str2[MAX] = { 0 };

    int loop; //loop counter
    int flag = 1;

    //declare & initialize pointer variables
    char* pStr1 = str1;
    char* pStr2 = str2;

    //read strings
    printf("Enter string 1: ");
    scanf("%[^\n]s", pStr1);
    printf("Enter string 2: ");
    getchar(); //read & ignore extra character
    scanf("%[^\n]s", pStr2);

    //print strings
    printf("string1: %s\nstring2: %s\n", pStr1, pStr2);

    //comparing strings
    for (loop = 0; (*(pStr1 + loop)) != '\0'; loop++) {
        if (*(pStr1 + loop) != *(pStr2 + loop)) {
            flag = 0;
            break;
        }
    }

    if (flag)
        printf("Strings are same.\n");
    else
        printf("Strings are not same.\n");

    return 0;
}

Output

First run:
Enter string 1: IncludeHelp.com 
Enter string 2: Include.com 
string1: IncludeHelp.com
string2: Include.com
Strings are not same.

Second run:
Enter string 1: includehelp.com 
Enter string 2: includehelp.com 
string1: includehelp.com
string2: includehelp.com
Strings are same.

Here, flag is a variable that is assigned by 1 initially, within the loop if any character of first string is not equal to character of second string, and then value of flag will be 0 (loop will be terminated). At the end, we will check if flag is 1, strings are same else strings are not same.

In this example, we have used the following C language topics that you should learn: