Find the bug in this code.

Question

This is a code to to find happy numbers.I don't know what's wrong with it.Please explain..
https://code.sololearn.com/c4Eyj1khqFnV/?ref=app

Answer 1

Look at line number 14 , you are actually going to print address of n , not n.

In function get_digit , variable 'a' is not declared .

Answer 2

But variable a declared as global variable.Is it necessary to declare in the function also?