Package g0301_0400.s0338_counting_bits

Class Solution

  • All Implemented Interfaces:
    
public final class Solution

    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:

    • <code>0 <= n <= 10<sup>5</sup></code>

    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++)?

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description

    • Field Summary

      Fields 
      Modifier and Type Field Description

    • Constructor Summary

      Constructors 
      Constructor Description
      Solution()

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      final IntArray countBits(Integer num)

      • Methods inherited from class java.lang.Object

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