Palindrome program in C++

Palindrome number program in C++

If a number remains the same when reversed, it is known as a palindrome number.

There are two ways through which we can do this.

• Using string reverse method
• Use of modulo operator

Using string reverse method

Algorithm:

1. Convert number to a string
2. Copy that string to another string
3. Reverse the string
4. Compare the reversed string and the original string

Code:

#include<iostream>
#include<cstring> //string library
#include <algorithm> //library containing begin() and end()
using namespace std;
int main()
{
int number,remainder;
cin>>number;
string s1=to_string(number);//storing string value of number in s1
string s2=s1;//copy contents of s1
reverse(s2.begin(), s2.end()); //reversing the complete string s2
if(s1==s2)
cout<<"palindrome";
else
cout<<"not a palindrome";
return 0;
}

Advantage:

• Easy to understand and execute

Disadvantage:

• Wastage of more memory due to conversion in string

Using modulo operator

Algorithm:

1. Save the number in another variable for future use.
2. Now, reverse the number using while loop.
3. Compare the reversed number and the original number.

Code:

#include<iostream>
using namespace std;
int main()
{
int num,rem;
cin>>num;
int duplicatenum=num;
int newnum=0;
while(num!=0) // till all digits of num are dealt with
{
rem=num%10; //remainder,last digit extracted
newnum=newnum*10+rem; // connect rem to newnum
num=num/10; //trimming last digit from num
}
if(newnum==duplicatenum)
cout<<"palindrome";
else
cout<<"not a palindrome";
return 0;
}

Advantage:

• Faster execution
• Uses less space