14 Days Study Plan to Crack Algo I

Day 13

231. Power of Two

Given an integer n, return true if it is a power of two. Otherwise, return false.

An integer n is a power of two, if there exists an integer x such that n == 2x.

Example 1:

Input: n = 1
Output: true
Explanation: 20 = 1

Example 2:

Input: n = 16
Output: true
Explanation: 24 = 16

Example 3:

Input: n = 3
Output: false


  • -231 <= n <= 231 - 1

Follow up: Could you solve it without loops/recursion?

Bit Solution https://leetcode.com/problems/power-of-two/discuss/369024/100-fastest-0ms-one-line-solution-with-explanation-binary-trick

191. Number of 1 Bits

Write a function that takes an unsigned integer and returns the number of ‘1’ bits it has (also known as the Hamming weight).


  • Note that in some languages, such as Java, there is no unsigned integer type. In this case, the input will be given as a signed integer type. It should not affect your implementation, as the integer’s internal binary representation is the same, whether it is signed or unsigned.
  • In Java, the compiler represents the signed integers using 2’s complement notation. Therefore, in Example 3, the input represents the signed integer. -3.

Example 1:

Input: n = 00000000000000000000000000001011
Output: 3
Explanation: The input binary string 00000000000000000000000000001011 has a total of three '1' bits.

Example 2:

Input: n = 00000000000000000000000010000000
Output: 1
Explanation: The input binary string 00000000000000000000000010000000 has a total of one '1' bit.

Example 3:

Input: n = 11111111111111111111111111111101
Output: 31
Explanation: The input binary string 11111111111111111111111111111101 has a total of thirty one '1' bits.


  • The input must be a binary string of length 32.

Follow up: If this function is called many times, how would you optimize it?

Bit solution: https://leetcode.com/problems/number-of-1-bits/discuss/921847/Three-JS-solutions




Consistency achieves everything https://github.com/paigekim29

Love podcasts or audiobooks? Learn on the go with our new app.

Recommended from Medium

Feeds with Real-time Signals (Home Feed — Part 2)

Changing Careers, Or How I Learned to Stop Worrying and Love Code

Testing Ubuntu 20.04

A Byte of Coding Issue #101

Deverse World Pre-Alpha 1.0.0

Deploying WordPress with MySQL on Top of Amazon EKS

PVS-Studio in the Clouds: Azure DevOps

(Windows) Run Video Chat within your Unity application

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store
Joo Hee Paige Kim

Joo Hee Paige Kim

Consistency achieves everything https://github.com/paigekim29

More from Medium

The Blind 75 Leetcode Series: Valid Parentheses

Solutions for LeetCode 743

204. Count Primes

LeetCode — Longest Common Sequences