338. Counting Bits
Difficulty: Medium
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:
Input: 2
Output: [0,1,1]
Example 2:
Input: 5
Output: [0,1,1,2,1,2]
Solution
Language: C++
class Solution {
public:
vector<int> countBits(int num) {
vector<int> bits(num+1, 0);
for (int i = 1; i <= num; i++)
bits[i] = bits[i & (i-1)] + 1;
return bits;
}
};