Package g0301_0400.s0338_counting_bits

Class Solution

java.lang.Object
g0301_0400.s0338_counting_bits.Solution
public class Solution extends java.lang.Object
338 - Counting Bits.

Easy

Given an integer n, return an array ans of length n + 1 such that for each i (0 <= i <= n), ans[i] is the number of 1’s in the binary representation of i.

Example 1:

Input: n = 2

Output: [0,1,1]

Explanation:

 0 --> 0
 1 --> 1
 2 --> 10

Example 2:

Input: n = 5

Output: [0,1,1,2,1,2]

Explanation:

 0 --> 0
 1 --> 1
 2 --> 10
 3 --> 11
 4 --> 100
 5 --> 101

Constraints:

  • 0 <= n <= 105

Follow up:

  • It is very easy to come up with a solution with a runtime of O(n log n). Can you do it in linear time O(n) and possibly in a single pass?
  • Can you do it without using any built-in function (i.e., like __builtin_popcount in C++)?

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int[]
    countBits(int num)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • countBits

      public int[] countBits(int num)