Convert to Base -2

LeetCode Q 1017 - Convert to Base -2

Given a number N, return a string consisting of “0”s and “1”s that represents its value in base -2 (negative two).

The returned string must have no leading zeroes, unless the string is “0”.

Example 1: Input: 2 ; Output: "110"
Explantion: (-2) ^ 2 + (-2) ^ 1 = 2
Example 2: Input: 3; Output: "111"
Explantion: (-2) ^ 2 + (-2) ^ 1 + (-2) ^ 0 = 3
Example 3: Input: 4 ; Output: "100"
Explantion: (-2) ^ 2 = 4

Note: 0 <= N <= 10^9

Solution

Code:

private static final int BASE = -2;

public String baseNeg2(int N) {
  if (N == 0) return "0";
  
  StringBuilder sb = new StringBuilder();
  while (N != 0) {
    int r = N % BASE;
    N /= BASE;
    if (r < 0) {
        r += Math.abs(BASE);
        N++;
    }
    sb.append(r);
  }
  
  return sb.reverse().toString();
}