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C Program to Compare Two Strings



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In this article, you will learn and get code about checking whether the two input strings are equal or not with and without using standard library function.

without using strcmp() Function

This program will not use any standard library function say strcmp() that helps while comparing two string in C. Rather this program will compare the two given string by user with the help of self-defined code. Let's have a look at it:

// Compare Two Strings without using Library function
// -------codescracker.com-------

#include<stdio.h>
#include<conio.h>
int main()
{
    char str1[50], str2[50];
    int i=0, chk=0;
    printf("Enter First String: ");
    gets(str1);
    printf("Enter Second String: ");
    gets(str2);
    while(str1[i]!='\0' || str2[i]!='\0')
    {
        if(str1[i]!=str2[i])
        {
            chk = 1;
            break;
        }
        i++;
    }
    if(chk==0)
        printf("\nStrings are Equal");
    else
        printf("\nStrings are not Equal");
    getch();
    return 0;
}

This program was compiled and executed in Code::Blocks IDE. On executing the above program, you will see the output as shown in the snapshot given below:

c program compare strings

Now supply any two string say codes and cracker and press ENTER key to see the output as shown here in the snapshot given below:

c program compare two strings

Let's take another sample run, in which let's suppose that user has provided two equal string say codes and codes.

compare two string program c

Let's take a look at some of the main logic used in above program.

Logic used in previous Program

Here are the list of some main logic used in previous program:

For example, let's suppose that if user enters codes and cracker as two input string. So the dry run of the above program using these two given string (as input) is given below:

using Library Function

Let's create another simple program that that also checks whether the given two strings are equal or not using standard library function of C:

// Compare Two Strings in C using Library Function
// -------codescracker.com-------

#include<stdio.h>
#include<conio.h>
#include<string.h>
int main()
{
    char str1[50], str2[50];
    int len1, len2;
    printf("Enter First String: ");
    gets(str1);
    printf("Enter Second String: ");
    gets(str2);
    len1 = strlen(str1);
    len2 = strlen(str2);
    if(len1==len2)
    {
        if(strcmp(str1, str2)==0)
            printf("\nStrings are Equal");
        else
            printf("\nStrings are not Equal");
    }
    else
        printf("\nStrings are not Equal");
    getch();
    return 0;
}

This program will produce the same output as of previous program. In above program, first we have checked whether the length of both the string is equal or not, if it is equal then process further. Otherwise if length of the given two strings is not equal, then obviously both the strings will not be equal.

Note - If both strings are equal, then strcmp() function returns 0. Otherwise, if both strings are not equal, then strcmp() function returns 1

Same Program in Other Languages


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