【LeetCode】Counting Bits（338）

1. Description

　　Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1‘s in their binary representation and return them as an array.

　　Example:
　　For num = 5 you should return [0,1,1,2,1,2].

2. Answer　

public class Solution {
    public int[] countBits(int num) {
        int[] result = new int[num + 1];
        for (int i = 1; i <= num; i++) {
            result[i] = result[i & (i - 1)] + 1;
        }

        return result;
    }
}