How the following Decimal to Binary conversion code is working?

Question

I came across the following C++ code in the InterviewBit for the decimal to binary conversion as displayed in the below image.

class Solution{

public:
  string findDigitsInBinary(int n){
    string ans;
    if(n == 0) return "0";

    while(n > 0){
      int rem = n % 2;
      ans.push_back((char)('0' + rem));
      n /= 2;
    }

    reverse(ans.begin(), ans.end());
    return ans;
  }
};

I am unable to understand what is happening in the second statement of the while loop.

ans.push_back((char)('0' + rem));

Here is my interpretation of this code.

Suppose I take the value of n as 5.

Now for the first iteration of while loop, 5 > 0.
rem = 5%2 = 1;
In the ans string, '0' + 1(rem) i.e. "01" will be stored.
n = 5/2 = 2
Now, for second iteration, 2 > 0.
rem = 2 % 2 = 0
ans = "01" (already stored) + '0' + '0'(rem) => "0100"
n = 2/2 = 1
In final iteration, 1 > 0.
rem = 1 % 2 = 1
ans = "0100" + '0' + 1(rem) => "010001"
n = 1 / 2 = 0
Now on reversing the answer, it will become => 100010 but it is not the correct answer.

So, can anyone please explain where I am wrong?

since `rem = n % 2;` so it can be either `0` or `1`, `ans.push_back()` is going to take a `char` and with that char you're either adding `0` to it or `1`. `'0' + 0` gives `'0'` and `'0' + 1` gives `'1'`. — Abhinav Gauniyal, Feb 21 '17 at 10:11
As frequently seen in questions with this title, there is no decimal to binary conversion here. There is *binary* to ASCII-encoded binary. — user207421, Apr 23 '18 at 02:24

score 4 · Accepted Answer · edited May 23 '17 at 12:09

4

'0' + rem is not doing what you think: '0' is a char literal and rem is an int value. Adding them together will result in an int that represents the ASCII value of either '0' or '1'.

More information: "Convert an int to ASCII character"

edited May 23 '17 at 12:09

Community

1
1

answered Feb 21 '17 at 10:03

Vittorio Romeo

90,666
33
258
416

How the following Decimal to Binary conversion code is working?

1 Answers1