// University of Iowa
// 22C-30 Homework 3
// Problem 3

// by: Justin C. Miller
// Prof: Sriram

// Description: recursive function
//              to computer binary
//              equivalent of a given
//              positive integer n

#include <iostream>// for cout, cin
#include <cstdlib> // for EXIT_SUCCESS
#include <string>  // for string

using namespace std; // so there's no std::cin

string binaryEquivalent(int) ;

int main(int argc, char * argv[]){
  for(int i = 0 ; i < 32 ; i++)
     cout << i << " in binary is " 
          << binaryEquivalent(i) << endl ;
  return EXIT_SUCCESS ;
}//end of main function

// PRE- given a positive integer n
// POST- returns binary equivalent of
//       of n in string format
string binaryEquivalent(int n){
  if(n < 0){
    cerr << "Binary Equivalent only" 
         << "  works w/ positive integers"<< endl ;
    exit(EXIT_FAILURE) ;
  }else if(n == 0){
    return "0" ;  // required only for n = 0
  }else if(n == 1){
    return "1" ;  // base case
  }else if(n % 2 == 0){ 
    return binaryEquivalent(n/2) + "0" ; // even
  }else{ 
    return binaryEquivalent(n/2) + "1" ; // odd
  }//else
}//end of binaryEquivalent function