Counting Bits
Desicription
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 1:
代码语言：javascript复制Input: 2
Output: [0,1,1]Example 2:
代码语言：javascript复制Input: 5
Output: [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.
Solution
代码语言：javascript复制class Solution {
public:
std::vector<int> countBits(int num) {
auto res = std::vector<int>(num 1);
for(int i = 0; i <= num; i ) {
res[i] = res[i >> 1] (i & 1);
}
return res;
}
};
