Bitwise AND of Numbers Range

Given a range [m, n] where 0 <= m <= n <= 2147483647, return the bitwise AND of all numbers in this range, inclusive.

For example, given the range [5, 7], you should return 4.

Solution:

  1. public class Solution {
  2.   public int rangeBitwiseAnd(int m, int n) {
  3.     return rangeBitwiseAnd(m, n, 0x80000000);
  4.   }
  6.   int rangeBitwiseAnd(int m, int n, int shift) {
  7.     // edge case
  8.     if (m == 0) return 0;
  10.     // find highest bit of m
  11.     while ((shift & m) == 0) {
  12.       if ((shift & n) != 0) return 0;
  13.       shift >>>= 1;
  14.     }
  16.     return shift + rangeBitwiseAnd(m - shift, n - shift, shift);
  17.   }
  18. }