g0301_0400.s0338_counting_bits

Class Solution

java.lang.Object

g0301_0400.s0338_counting_bits.Solution

public class Solution
extends 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 and Description
Solution()

Method Summary

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

Methods inherited from class java.lang.Object

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

Constructor Detail

Solution

public Solution()

Method Detail

countBits

public int[] countBits(int num)