Reversing Decimal to Binary Conversion Result [Closed]

Question

I'm trying to convert integers to binary, using the modulo operator. I get the correct digits, although they are in the incorrect order. For example 76 to binary is 1001100 but the output is 0011001; hence, I have tried to rectify this by outputting 1 if the result is 0 and outputting out 0 if the result is 1, using if-else statements; but the result is then 1100110, which is also wrong.

Here is my code:

include <iostream>
using namespace std;

int main() {

    int num;
    int remainder;

    cout << "Enter a decimal number:" << endl;
    cin >> num;
    
    while (num != 0){
        remainder = num % 2;
        if (remainder == 1 ){
            cout << remainder - 1;
        }
        else if (remainder == 0){
            cout << remainder + 1;
        }
        num = num / 2;
    }
    return 0;
}

Any suggestions?

Accepted Answer

Rather than flipping the individual output digits, you need to reverse their order. There are many ways you can do this but one quite 'natural' method is to use a stack – which is an inherently last-in, first-out (LIFO) system.

The C++ Standard Template Library provides a std::stack container, ready-to-use. Here's a working program that does what you want:

#include <iostream>
#include <stack>
using std::cout, std::cin, std::endl; // Pre-C++17, these will need to be separate "using" lines!
using std::stack;

int main()
{
    int num;
    int remainder;
    stack<char> digits;

    cout << "Enter a decimal number:" << endl;
    cin >> num;

    while (num != 0) { // Push the digits onto the stack ...
        remainder = num % 2;
        digits.push(remainder ? '1' : '0');
        num = num / 2;
    }
    while (!digits.empty()) { // ... then print and pop them (in reverse order)
        cout << digits.top();
        digits.pop();
    }
    cout << endl;
    return 0;
}

Answer 2

You can use std::bitset. But if you want to do this without using std::bitset, you can push bits to string and reverse it.

Solution without Bitset

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

int main() {
  int N, i = 0; 
  
  std::cout << "Enter a decimal number:" << std::endl;
  std::cin >> N;

  std::string res(32, '0');
  while (N) {
    res[i++] += (N&1);
    N >>= 1;  
  }

  std::reverse(res.begin(), res.end());
  std::cout << res << std::endl;
}

Solution With Bitset

#include <iostream>
#include <bitset>

int main() {
  int N; 
  
  std::cout << "Enter a decimal number:" << std::endl;
  std::cin >> N;

  std::cout << std::bitset<32>(N).to_string() << std::endl;
}

Reversing Decimal to Binary Conversion Result [Closed]

Must Read

2 Answers

Sarah Jenkins