C Program to Compare Two Strings

Write a C Program to Compare Two Strings without using strcmp function. There are multiple ways to compare two strings. However, we will discuss three different approaches: using For Loop, While Loop, and Functions in C Programming.

C Program to Compare Two Strings without using strcmp

This program allows users to enter two string values or a two-character array. Next, this compare strings program will use For Loop to iterate every character present in that string and compares individual characters. I suggest you refer to strcmp function.

/* without using strcmp() */
 
#include <stdio.h>
#include <string.h>

int main()
{
  	char Str1[100], Str2[100];
  	int result, i;
 
  	printf("\n Please Enter the First String :  ");
  	gets(Str1);
  	
  	printf("\n Please Enter the Second String :  ");
  	gets(Str2);
  	
  	for(i = 0; Str1[i] == Str2[i] && Str1[i] == '\0'; i++);
		   
  	if(Str1[i] < Str2[i])
   	{
   		printf("\n str1 is Less than str2");
	}
	else if(Str1[i] > Str2[i])
   	{
   		printf("\n str2 is Less than str1");
	}
	else
   	{
   		printf("\n str1 is Equal to str2");
	}
  	
  	return 0;
}

Let me insert two different strings

 Please Enter the First String :  cat

 Please Enter the Second String :  dog

 str1 is Less than str2

two more different strings

 Please Enter the First String :  John

 Please Enter the Second String :  Ani

 str2 is Less than str1

C Program to Compare Two Strings Using While Loop

This program is the same as above, but this time we are using a While loop. We replaced the For Loop in the above example with While Loop. I suggest you refer to While Loop to understand the C Programming loop Iteration.

/* using library function */
 
#include <stdio.h>
#include <string.h>

int main()
{
  	char Str1[100], Str2[100];
  	int result, i;
 	i = 0;
 	
  	printf("\n Please Enter the First :  ");
  	gets(Str1);
  	
  	printf("\n Please Enter the Second :  ");
  	gets(Str2);
  	
  	while(Str1[i] == Str2[i] && Str1[i] == '\0')
	  	i++;
		   
  	if(Str1[i] < Str2[i])
   	{
   		printf("\n str1 is Less than str2");
	}
	else if(Str1[i] > Str2[i])
   	{
   		printf("\n str2 is Less than str1");
	}
	else
   	{
   		printf("\n str1 is Equal to str2");
	}
  	
  	return 0;
}

 Please Enter the First :  hello

 Please Enter the Second :  hello

 str1 is Equal to str2

Compare Two Strings Using Functions

This C program is the same as the above example. However, this time, we are using the Functions concept to separate the logic from the main program.

We created a function compare_strings to compare the strings. Next, we are calling that function inside our main function.

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

int Compare_Strings(char *Str1, char *Str2);
 
int main()
{
  	char Str1[100], Str2[100];
  	int result;
 
  	printf("\n Please Enter the First :  ");
  	gets(Str1);
  	
  	printf("\n Please Enter the Second :  ");
  	gets(Str2);
  	
  	result = Compare_Strings(Str1, Str2);
  	
  	if(result < 0)
   	{
   		printf("\n str1 is Less than str2");
	}
	else if(result > 0)
   	{
   		printf("\n str2 is Less than str1");
	}
	else
   	{
   		printf("\n str1 is Equal to str2");
	}
  	
  	return 0;
}
int Compare_Strings(char *Str1, char *Str2)
{
	int i = 0;
  	while(Str1[i] == Str2[i])
  	{
  		if(Str1[i] == '\0' && Str2[i] == '\0')
	  		break;
		i++;
	}
	return Str1[i] - Str2[i];
}

 Please Enter the First :  program

 Please Enter the Second :  program

 str1 is Equal to str2