原题:
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.
题意为:给定一个非负的整数num,对于0<=i<=num的i,计算i对应二进制数中1的个数,并以数组的形式返回
Java 实现:
public class Solution {
public int[] countBits(int num) {
int[] result = new int[num+1];
for (int i = 0; i <= num; i++) {
int temp= i;
int c=0;
String s = Integer.toBinaryString(temp);
for (int j = 0; j < s.length(); j++) {
if(s.charAt(j)=='1') c++;
}
result[i]=c;
}
return result;
}
}