【LeetCode】338. Counting Bits

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].

Follow up:

• It is very easy to come up with a solution with run time O(n*sizeof(integer)). But can you do it in linear time O(n) /possibly in a single pass?
• Space complexity should be O(n).
• Can you do it like a boss? Do it without using any builtin function like __builtin_popcount in c++ or in any other language.

Credits:
Special thanks to @ syedee for adding this problem and creating all test cases.

这个完全搞不懂呢。。

参考了这位的代码

http://www.cnblogs.com/HellcNQB/p/5361593.html

/** * @param {number} num * @return {number[]}  */var countBits = function(num) {        var ret=new Array(num + 1);    ret[0]=0;    for (var i = 1; i <= num; ++i)        ret[i] = ret[i&(i - 1)] + 1;    return ret;};