Matlab-Palindrome Checker: Check if a Number is Palindrome or Not

[Raghav Gupta]

Homework Statement

Check if a number is palindrome or not.

Homework Equations

Writing down the code in attempt.

The Attempt at a Solution

x=input('Enter number: ');
temp=x;
rev=0;
while(temp>0)
    a=mod(temp,10);
    rev=rev*10+a;
    temp=temp/10;
end
disp('The reversed number is');
disp(rev);
if(rev==x)
    disp('The number is palindrome');
else
    disp('The number is not palindrome');
end

Result I am getting

Enter number: 66
The reversed number is
   Inf

The number is not palindrome

What is the error here?

 

[Mark44]

Homework Statement

Check if a number is palindrome or not.

Homework Equations

Writing down the code in attempt.

The Attempt at a Solution

x=input('Enter number: ');
temp=x;
rev=0;
while(temp>0)
    a=mod(temp,10);
    rev=rev*10+a;
    temp=temp/10;
end
disp('The reversed number is');
disp(rev);
if(rev==x)
    disp('The number is palindrome');
else
    disp('The number is not palindrome');
end

Result I am getting

Enter number: 66
The reversed number is
   Inf

The number is not palindrome

What is the error here?

Using your example of 66, which is clearly a palindromic number, hand simulate your code to see what it is doing. Take a close look at this section:

x=input('Enter number: ');
temp=x;
rev=0;
while(temp>0)
    a=mod(temp,10);
    rev=rev*10+a;
    temp=temp/10;
end

 

[Raghav Gupta]

Using your example of 66, which is clearly a palindromic number, hand simulate your code to see what it is doing. Take a close look at this section:

x=input('Enter number: ');
temp=x;
rev=0;
while(temp>0)
    a=mod(temp,10);
    rev=rev*10+a;
    temp=temp/10;
end

The thing is that if the datatype of all the variables is int then it works perfectly fine , the method.
In MATLAB we cannot declare variable datatype unlike c++. That should be the error as MATLAB is taking in account double datatype?

 

[Raghav Gupta]

Also How can I write code of MATLAB here in PF like you have did?
I don't see MATLAB code language in toolbar

 

[Mark44]

The thing is that if the datatype of all the variables is int then it works perfectly fine , the method.
In MATLAB we cannot declare variable datatype unlike c++. That should be the error as MATLAB is taking in account double datatype?

If you entered 66, and MATLAB said that the reversed number is Inf, then it doesn't seem that you code is working.

Did you try what I suggested, of going through your code by hand to see what it produces?

Alternatively, you can add printf() statements in your code to see the values of a, rev, and temp in the loop.

Also How can I write code of MATLAB here in PF like you have did?
I don't see MATLAB code language in toolbar

I type [code=matlab] at the top and [/code] at the bottom.

 

[Raghav Gupta]

If you entered 66, and MATLAB said that the reversed number is Inf, then it doesn't seem that you code is working.

Did you try what I suggested, of going through your code by hand to see what it produces?

Yes I went through by hand and did operation on 66.
Let's say x=66
then temp= x = 66.
rev =0
Loop starts stating that If temp is greater then zero then continue loop.
a= mod(66, 10) = 6
rev= rev*10 + a= 0*10 + 6 =6
temp= temp/10= 66/10 = 6.
Since, temp = 6>0 loop again runs
a= mod(6,10) = 6
rev = 6*10 + a = 60 + 6=66
temp = 6/10 = 0. And then loop stops.
So finally value of rev should be 66. But then also why my code is showing rev as inf?
I tried this program in C++ with same logic and there it was running perfectly well

#include<iostream.h>
#include<conio.h>
void main(){
clrscr();
int x, temp, rev=0, a;
cout<<" Enter a number\n";
cin>>x;
temp=x;
while( temp> 0){
a = temp%10;
rev= rev*10 + a;
temp= temp/10;
}
if(rev==x)
cout<<"\nThe number is palindrome";
else
cout<<"\nThe number is not palindrome";
getch();
}

 

[DrClaude]

temp = 6/10 = 0.

That's not correct. temp = 0.6

I tried this program in C++ with same logic and there it was running perfectly well

Because you declared temp as an int. There is no such thing in Matlab, so temp will store the floating-point result.

 

[Raghav Gupta]

That's not correct. temp = 0.6Because you declared temp as an int. There is no such thing in Matlab, so temp will store the floating-point result.

So how can I correct that in matlab?

 

[DrClaude]

To duplicate the behavior of C++, use temp = floor(temp/10). I think that changing the while to while(temp > 1) is a more elegant solution.

 

[Raghav Gupta]

To duplicate the behavior of C++, use temp = floor(temp/10).

Yes Now the program is working properly. Floor function works as a greatest integer function here.

I think that changing the while to while(temp > 1) is a more elegant solution.

No it is not since when we give input as 121 , the reversed number comes as 12.

 

[DrClaude]

Yes Now the program is working properly. Floor function works as a greatest integer function here.

No it is not since when we give input as 121 , the reversed number comes as 12.

Yes. I meant >= 1.

 

[Mark44]

So how can I correct that in matlab?

Use div, the MATLAB integer division operator. See http://www.mathworks.com/help/symbolic/mupad_ref/div.html