Write a C program to check whether a given string is a palindrome or not.

 Write a C program to check whether a given string is a palindrome or not?

A string could be a Palindrome string in C if it remained the same when we reversed it. Let us see how to write a C Program to Check the Given String is Palindrome using Built-in functions, and without using built-in functions.

This program for string palindrome in c allows the user to enter a string (or character array), and a character value. Next, it will check whether the user-specified string is a palindrome string or not.

/* C Program to Check the given string is Palindrome or not */
 
#include <stdio.h>
#include <string.h>
 
int main()
{
  	char str[100];
  	int i, len, flag;
  	flag = 0;
 
  	printf("\n Please Enter any String :  ");
  	gets(str);
  	
  	len = strlen(str);
  	 	   	
  	for(i = 0; i < len; i++)
	{
		if(str[i] != str[len - i - 1])
		{
			flag = 1;
			break;	
		} 
	}
	if(flag == 0)
	{
		printf("\n %s is a Palindrome String", str);
	}
	else
	{
		printf("\n %s is Not a Palindrome String", str);
	}	
	
  	return 0;
}

ANALYSIS

Here, we used For loop to iterate every character in a String, and check the palindrome condition
for(i = 0; i < len; i++)
{
if(str[i] != str[len - i - 1])
{
flag = 1;
break;
}
}
len = 3
Flag = 0

str[] = wow

For Loop – First Iteration: for(i = 0; i < len ; i++)
The condition is True because 0 < 3.

Within the For Loop we used If statement to check whether the str[1] is not equal to str[len – i – 1]
if(str[i] != str[len – i – 1]) => if(str[0] != str[3 – 0 – 1])
if(w != w) – Condition is False. So, Flag is still 0

Second Iteration: for(i = 1; 1 < 3 ; 1++)
if(str[i] != str[len – i – 1]) => if(str[1] != str[3 – 1 – 1])
if(o != o) – Condition is False. So, Flag is still 0

Third Iteration: for(i = 2; 2 < 3 ; 2++)
if(str[i] != str[len – i – 1]) => if(str[2] != str[3 – 2 – 1])
if(w != w) – Condition is False. So, Flag is still 0

Program to Check the Given String is Palindrome using  Built-in Functions

In this string palindrome program, we are using the built-in functions strcpy, strrev, and strcmp.

First, the C programming strcpy copies the user given string to a new string. Next, we used the strive to reverse the string. And finally, we used strcmp to compare the original string with the reverse one.

/* C Program to Check the given string is Palindrome or not */
 
#include <stdio.h>
#include <string.h>
 
int main()
{
  	char str[100], revstr[100];
  	int flag;
 
  	printf("\n Please Enter any String :  ");
  	gets(str);

  	// To Copy the string to revstr
  	strcpy(revstr, str);

  	strrev(revstr); // reverse the string

  	// Comparing string
	flag = strcmp(str, revstr); 

	if(flag == 0)
	{
		printf("\n %s is a Palindrome String", str);
	}
	else
	{
		printf("\n %s is Not a Palindrome String", str);
	}	
	
  	return 0;
}

What do you think?

I hope, now you have a better understanding of palindrome Comments and suggestions regarding this article are welcome.