Problem $2$: Implement a Recursive Conversion Function $(15$ points$)$

Write a program which defines a recursive function that takes a decimal integer as a parameter and outputs the binary equivalent as a string.$$ The function should output the binary value of the integer one digit at a time.$$ If the integer is even, capture a zero and call the function with the value divided by two; if the integer is odd, capture a one, and do the same.$$ When the function returns to the caller, reverse the captured values to obtain the correct binary representation.

For example, if the input were $42$ decimal, the final result would be $101010$ binary.$$ Leading zeros should be suppressed.