C Program to Compare Two Strings

Write a C Program to Compare Two Strings without using the 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 compares strings program will use For Loop to iterate every character present in that string and compare individual characters. I suggest you refer to the 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 we are using a While loop this time. 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;
}

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 call 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];
}