Palindrome is a number or sequence of characters which reads same backward and forward. If we reverse a palindrome number, the reversed and original number will be same. The first C program checks whether a number is palindrome by reversing the number. The second program does the same thing without reversing the number.
By reversing the number:
#include <stdio.h>
int reverse(int n)
{
int r = 0;
while(n)
{
r = r * 10 + n % 10;
n = n / 10;
}
return r;
}
void main()
{
int num = 0;
printf("Enter an integer: ");
scanf("%d", &num);
if(num == reverse(num))
printf("%d is palindrome\n", num);
else
printf("%d is not palindrome.\n", num);
}
Without reversing the number
#include <stdio.h>
#include <math.h>
int getdigit(int num, int n)
{
int r, t1, t2;
t1 = pow(10, n+1);
r = num % t1;
if (n > 0)
{
t2 = pow(10, n);
r = r / t2;
}
return r;
}
int number_len(int n)
{
int len = 0;
while(n)
{
len++;
n /= 10;
}
return len;
}
void main()
{
int num = 0, i, len, flag = 1;
printf("Enter an integer: ");
scanf("%d", &num);
len = number_len(num);
for (i = 0; i < len/2; i++)
{
if(getdigit(num, i) != getdigit(num, len - i - 1))
{
flag = 0;
break;
}
}
if(flag)
printf("%d is palindrome.\n", num);
else
printf("%d is not palindrome.\n", num);
}
Outout:
Enter an integer: 4232 4232 is not palindrome. Enter an integer: 65756 65756 is palindrome.
