Sunday, December 2

Program to Check Given String is a Palindrome


Write a C program to check whether the given string is a palindrome.

Palindrome is a string, which when read in both forward and backward way is same.
Example: radar, madam, pop, lol, Malayalam etc.,

Program:

#include <stdio.h>
#include <string.h>
int main() 
{
char string1[20];
int i, length;
int flag = 0;
printf("Enter a string: \n");
scanf("%s", string1);
length = strlen(string1);
for(i=0;i < length ;i++)
   {
       if(string1[i] != string1[length-i-1])
   {
       flag = 1;
       break;
    }
    }
if (flag) 
{
       printf("%s is not a palindrome\n", string1);
 }
else 
{
      printf("%s is a palindrome\n", string1);
 }
return 0;
}


Output:
Enter a string: radar
"radar" is a palindrome

Explanation with example:
To check if a string is a palindrome or not, a string needs to be compared with the reverse of itself.
Consider a palindrome string: "radar",
---------------------------
index: 0 1 2 3 4
value: r a d a r
---------------------------
To compare it with the reverse of itself, the following logic is used:
0th character in the char array, string1 is same as 4th character in the same string.
1st character is same as 3rd character.
2nd character is same as 2nd character.
. . . .
ith character is same as 'length-i-1'th character.
If any one of the above condition fails, flag is set to true(1), which implies that the string is not a palindrome.
By default, the value of flag is false(0). Hence, if all the conditions are satisfied, the string is a palindrome.