Code to concatenate two numbers' bits not working

Question

The task is to concat the binary of 2 given numbers.

Example:

Given 5 (101) and 3 (011),

Answer 1

I don't know what language you are using, it's almost Java, so I am going with that.

This returns the result you are asking for, though you haven't given rules for determining how you know that 3 should be 011 instead of 11.

I have made the assumption that you want to assume that both numbers have the same number of bits, so 3 is 011 because 5 requires 3 bits.

public class Concat {
  public static void main(String[] args) {
    System.out.println( joinNums(3,5) );
  }

  public static int numBits( int n ) { 
    return (int)Math.ceil( Math.log(n) / Math.log(2) );
  }

  public static int joinNums( int num1 , int num2 ) {
    int bits = Math.max( numBits(num1) , numBits(num2) );
    return (num1 << bits) + num2;
  }
}