Anything wrong in this decimal to binary conversion?-CodePudding

I'm a college student and I have recently started learning c . I learned few syntaxes and I wrote a code which converts a decimal number to binary.

#include <iostream>
#include <string>

using namespace std;


void main()
{
    int num = 0, bit = 0, div = 0, i = 0;
    string binary = "";
    cout << "Enter a decimal number : ";
    cin >> num;
    div = num / pow(2, i);
    while (div != 0)
    {
        bit = div % 2;
        binary = to_string(bit)   binary;
        i  ;
        div = num / pow(2, i);
    }
    cout << "Binary of decimal " << num << " is : \n";
    cout << binary;


}

Can someone guide me if this code can be further optimized or if I have used a functions which is advised not to use. Thanks

My results were what I expected it to be, but I dont know if there is something else I should have tried.

CodePudding user response：

std::string toBinaryString(int n)
{
    if (n < 0){
        if (n == INT_MIN){
            // Negation of INT_MIN is UB on 2's complement systems.
            // Needs to be handled separately.
            return "Something";
        }
        return "-"   toBinaryString(-n);
    } else if (n > 0){
        std::string s;
        while (n){
            s = (n % 2 ? "1" : "0")   s;
            n /= 2;
        }
        return s;
    } else {
        return "0";
    }
}

is one way. It burns the CPU a little with the string prepending but the number of times that happens is binary logarithmic on n. The specific handling of 0 is ugly, but really that stems from the fact that generating zero from any numeral system is a pain. (The Romans didn't come up with anything.) Don't forget to check the return value of cin >> num in production code.

CodePudding user response：

A straightforward example of building up a string "backwards" from the smallest digit first using % and /=, and then using std::reverse to reverse that string. Specifically does not deal with signed ints.

#include <string>
#include <sstream>
#include <iostream>
#include <algorithm>

std::string convert_dec_to_bin(unsigned int dec) {
  if (dec == 0) return "0";

  std::stringstream ss;

  while (dec > 0) {
    ss << dec % 2;
    dec /= 2;
  }

  auto result = ss.str();

  std::reverse(result.begin(), result.end());

  return result;
}

int main() {
  unsigned int num;

  std::cin >> num;
  std::cout << convert_dec_to_bin(num) << std::endl;

  return 0;
}

CodePudding user response：

You have to include math.h library and after i use this line div = div / 2

CodePudding user response：

It's better to have div as a running total instead of calculating it afresh from num each time

div = num;
while (div != 0)
{
    bit = div % 2;
    binary = to_string(bit)   binary;
    i  ;
    div = div / 2;
}

This avoids the problems that can happen when using pow for integer powers, and is more efficient as well.