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; } }
原文：http://www.cnblogs.com/leesf456/p/5349083.html