## Palindrome number:

palindrome number can also be definded as a number which is equal to number after reversing its digits.
Example: for e.g. input is 12121, and after reversal of its digits, input number will be 12121.

## Logic:

1.Input a number
2.Reverse its digits
3.match reversed number against input number

``````#include<stdio.h>
#include<conio.h>
int ispalindrome(int num);
int reverse(int n);
int rev=0,rem=0;
void main()
{
int num;
printf("n Enter a number: ");
scanf("%d",&num);
if(ispalindrome(num))
{
printf("n %d is palindrome number",num);
}
else
{
printf("n %d is not palindrome number,"num);
}
getch();
}

int ispalindrome(int num)
{
if(num==reverse(num))
{
return 1;
}
else
{
return 0;
}
}

int reverse(int n)
{
if(n)
{
rem=n%10;
rev=rev*10+rem;
reverse(n/10);
}
return rev;
}
``````

Ouput:

``````Enter a number: 10201
10201 is palindrome number
``````

## c program to find reverse of a number using recursion

``````#include<stdio.h>
#include<conio.h>
int reverse(int num);
void main()
{
int num, r=0;
printf("n Enter a number: ");
scanf("%d",&num);
r = reverse(num);
printf("n Reverse number = %d",r);
getch();

}
int rev = 0, rem = 0;
int reverse(int num)
{
if(num)   {
rem=num%10;
rev=rev*10+rem;
reverse(num/10);
}
return rev;
}
``````

Ouput:

``````Enter a number: 371
Reverse number = 173
``````

## Program

### C Program to reverse digits of a number using for loop

``````#include
#include
void main()
{
int val;
int rever=0, remain=0;
printf("\n Enter a number: ");
scanf("%d",&val);
for(;val>0;val=val/10)
{
remain = val%10;
rever = rever*10+remain;
}

printf("\n reverse of number is = %d",rever);
getch();
}
``````

### Output

``````Enter a number: 132
reverse of number is = 231
``````

## Program

### Program to reverse digits of a number using while loop in c

``````#include<stdio.h>
#include<conio.h>
void main()
{
int num;
int rev=0, rem=0;
printf("n Enter a number: ");
scanf("%d",&num);
while(num>0)
{
rem = num%10;
rev = rev*10+rem;
num = num/10;
}
printf("n reverse number = %d",rev);
getch();
}
``````

### Output

``````Enter a number: 123
Reverse number = 321
``````

## Program

### Program in C for reversal of digits of a number using do while loop

``````#include
#include
void main()
{
int val;
int rever=0, remain=0;
printf("\nEnter a number: ");
scanf("\n%d",&val);
do
{
remain = val%10;
rever = rever*10+remain;
val = val/10;
}while(val>0);

printf("\nreverse of the number = %d",rever);
getch();
}
``````

### Output

``````Enter a number: 254
reverse of the number = 452
``````

## Program

### C Program to find and print sum of square of even numbers

``````#include<stdio.h>
#include<conio.h>
void main()
{
int num, sum=0;
for(num=1; num<=10;num++)
{
if(num%2==0)
sum=sum+num*num;
}
printf("n Sum of square of first 10 even numbers: %d",sum);

getch();
}
``````

### Output

``````sum of first 10 even numbers: 220
``````

### Explanation

• This program calculates sum of those numbers which produces no remainder after dividing by 2 i.e.
even numbers

• Above program performs addition of square of first 10 even numbers i.e. sum of squares of 2,4,6,8,10

## Program

### C Program to find and print sum of square of odd numbers

``````#include<stdio.h>
#include<conio.h>
void main()
{
int num, sum=0;
for(num=1; num<=10;num++)
{
if(num%2!=0)
sum=sum+num*num;
}
printf("n Sum of square of first 10 odd numbers: %d",sum);

getch();
}
``````

### Output

``````sum of first 10 odd numbers: 165
``````

## c program to check whether given number is armstrong number or not using for loop

``````#include<stdio.h>
#include<conio.h>
void main()
{
int num, n, rem;
int cube=0, sum=0;
printf("n Enter a number: ");
scanf("%d",&num);
n = num;
for(;n>0;n=n/10)
{
rem = n%10;
cube = rem*rem*rem;
sum = sum + cube;
}
if(num==sum)
{
printf("n %d is armstrong number",num);
}
else
{
printf("n %d not armstrong number",num);
}
getch();
}
``````

Ouput:

``````Enter a number: 407
407 is armstrong number
``````

## C program to check armstrong number using recursive function or recursion

Armstrong number is an integer which has sum of cubes of its individual digits equal to the number itself.

Example: 0,1,153,370,..

## logic

• Seperate each digit of input integer and then calculate its cube.
• Add the cube of all digits
• check final sum against input integer

## Program

### program to check armstrong number using recursive function or recursion

``````#include<stdio.h>
#include<conio.h>
int armstrong(int num);
void main()
{
int num, n;
printf("n Enter a number: ");
scanf("%d", &num);
n = armstrong(num);
printf("n %d is armstrong number",n);
getch();
}
int armstrong(int num)
{
int s = 0;
if(num)
{
s = ((num%10)*(num%10)*(num%10)) + armstrong(num/10);
}
return s;
}
``````

### Output

``````
input = 407
output = (4*4*4) + (0*0*0) + (7*7*7)
input  number equals sum of cube of all its digits.
So 407 is armstrong number
``````

## Armstrong numbers:

Input : 153.
Calculating armstrong number: 153 =(1*1*1)+(5*5*5)+(3*3*3)= 1+125+27 =153

If input equals output, 153==153, 153 is armstrong number.

``````#include<stdio.h>
#include<conio.h>
void main()
{
int num, n, rem;
int cube=0, sum;
printf("n Armstrong numbers between 1 and 1000 are: n");
for(num=1;num<=1000;num++)
{
sum=0;
n=num;
while(n>0)
{
rem=n%10;
cube=rem*rem*rem;
sum=sum+cube;
n=n/10;
}
if(num==sum)
{
printf("n%d is armstrong number",num);
}
getch();
}
``````

Ouput:

``````Armstrong numbers between 1 and 1000 are:
1 is armstrong number
153 is armstrong number
370 is armstrong number
371 is armstrong number
407 is armstrong number
``````

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