Answer by Aleksandar BiĊĦevac for How to check if a number is a power of 2
This one returns if the number is the power of two up to 64 value ( you can change it inside for loop condition ("6" is for 2^6 is 64);const isPowerOfTwo = (number) => { let result = false; for (let...
View ArticleAnswer by ABHISHEK PARMAR for How to check if a number is a power of 2
in this approach , you can check if there is only 1 set bit in the integer and the integer is > 0 (c++).bool is_pow_of_2(int n){ int count = 0; for(int i = 0; i < 32; i++){ count += (n>>i...
View ArticleAnswer by Marcus Moo for How to check if a number is a power of 2
This is another method to do it as wellpackage javacore;import java.util.Scanner;public class Main_exercise5 { public static void main(String[] args) { // Local Declaration boolean ispoweroftwo =...
View ArticleAnswer by Anil Gupta for How to check if a number is a power of 2
I see many answers are suggesting to return n && !(n & (n - 1)) but to my experience if the input values are negative it returns false values.I will share another simple approach here since...
View ArticleAnswer by eraoul for How to check if a number is a power of 2
In C, I tested the i && !(i & (i - 1) trick and compared it with __builtin_popcount(i), using gcc on Linux, with the -mpopcnt flag to be sure to use the CPU's POPCNT instruction. My test...
View ArticleAnswer by jbat100 for How to check if a number is a power of 2
Mark gravell suggested this if you have .NET Core 3, System.Runtime.Intrinsics.X86.Popcnt.PopCountpublic bool IsPowerOfTwo(uint i){ return Popcnt.PopCount(i) == 1}Single instruction, faster than (x !=...
View ArticleAnswer by rhodan for How to check if a number is a power of 2
Improving the answer of @user134548, without bits arithmetic:public static bool IsPowerOfTwo(ulong n){ if (n % 2 != 0) return false; // is odd (can't be power of 2) double exp = Math.Log(n, 2); if (exp...
View ArticleAnswer by FReeze FRancis for How to check if a number is a power of 2
for any power of 2, the following also holds.n&(-n)==nNOTE: fails for n=0 , so need to check for itReason why this works is:-n is the 2s complement of n. -n will have every bit to the left of...
View ArticleAnswer by displayName for How to check if a number is a power of 2
The following addendum to the accepted answer may be useful for some people:A power of two, when expressed in binary, will always look like 1 followed by n zeroes where n is greater than or equal to 0....
View ArticleAnswer by Khaled.K for How to check if a number is a power of 2
Example0000 0001 Yes0001 0001 NoAlgorithmUsing a bit mask, divide NUM the variable in binaryIF R > 0 AND L > 0: Return FALSEOtherwise, NUM becomes the one that is non-zeroIF NUM = 1: Return...
View ArticleAnswer by Raz Megrelidze for How to check if a number is a power of 2
bool IsPowerOfTwo(int n) { if (n > 1) { while (n%2 == 0) { n >>= 1; } } return n == 1; }And here's a general algorithm for finding out if a number is a power of another number. bool...
View ArticleAnswer by Chethan for How to check if a number is a power of 2
Here is another method I devised, in this case using | instead of & :bool is_power_of_2(ulong x) { if(x == (1 << (sizeof(ulong)*8 -1) ) return true; return (x > 0) && (x<<1...
View ArticleAnswer by Prakash Jat for How to check if a number is a power of 2
return ((x != 0) && !(x & (x - 1)));If x is a power of two, its lone 1 bit is in position n. This means x â 1 has a 0 in position n. To see why, recall how a binary subtraction works. When...
View ArticleAnswer by sudeepdino008 for How to check if a number is a power of 2
int isPowerOfTwo(unsigned int x){ return ((x != 0) && ((x & (~x + 1)) == x));}This is really fast. It takes about 6 minutes and 43 seconds to check all 2^32 integers.
View ArticleAnswer by bugs king for How to check if a number is a power of 2
bool isPowerOfTwo(int x_){ register int bitpos, bitpos2; asm ("bsrl %1,%0": "+r" (bitpos):"rm" (x_)); asm ("bsfl %1,%0": "+r" (bitpos2):"rm" (x_)); return bitpos > 0 && bitpos == bitpos2;}
View ArticleAnswer by jerrymouse for How to check if a number is a power of 2
A number is a power of 2 if it contains only 1 set bit. We can use this property and the generic function countSetBits to find if a number is power of 2 or not.This is a C++ program:int...
View ArticleAnswer by abelenky for How to check if a number is a power of 2
bool isPow2 = ((x & ~(x-1))==x)? !!x : 0;
View ArticleAnswer by deft_code for How to check if a number is a power of 2
Here's a simple C++ solution:bool IsPowerOfTwo( unsigned int i ){ return std::bitset<32>(i).count() == 1;}
View ArticleAnswer by udhaya for How to check if a number is a power of 2
Find if the given number is a power of 2. #include <math.h>int main(void){ int n,logval,powval; printf("Enter a number to find whether it is s power of 2\n"); scanf("%d",&n);...
View ArticleAnswer by Matt Howells for How to check if a number is a power of 2
bool IsPowerOfTwo(ulong x){ return x > 0 && (x & (x - 1)) == 0;}
View ArticleAnswer by user134548 for How to check if a number is a power of 2
private static bool IsPowerOfTwo(ulong x){ var l = Math.Log(x, 2); return (l == Math.Floor(l));}
View ArticleAnswer by Andreas Petersson for How to check if a number is a power of 2
return (i & -i) == i
View ArticleAnswer by Michael Burr for How to check if a number is a power of 2
Some sites that document and explain this and other bit twiddling hacks...
View ArticleAnswer by configurator for How to check if a number is a power of 2
After posting the question I thought of the following solution:We need to check if exactly one of the binary digits is one. So we simply shift the number right one digit at a time, and return true if...
View ArticleAnswer by Greg Hewgill for How to check if a number is a power of 2
There's a simple trick for this problem:bool IsPowerOfTwo(ulong x){ return (x & (x - 1)) == 0;}Note, this function will report true for 0, which is not a power of 2. If you want to exclude that,...
View ArticleHow to check if a number is a power of 2
Today I needed a simple algorithm for checking if a number is a power of 2.The algorithm needs to be:SimpleCorrect for any ulong value.I came up with this simple algorithm:private bool...
View ArticleAnswer by vivek nuna for How to check if a number is a power of 2
It's very easy in .Net 6 now.using System.Numerics;bool isPow2 = BitOperations.IsPow2(64); // sets trueHere is the documentation.
View ArticleAnswer by Uche Igbokwe for How to check if a number is a power of 2
There is a one liner in .NET 6// IsPow2 evaluates whether the specified Int32 value is a power of two.Console.WriteLine(BitOperations.IsPow2(128)); // True
View ArticleAnswer by Yanara for How to check if a number is a power of 2
There were a number of answers and posted links explaining why the n & (n-1) == 0 works for powers of 2, but I couldn't find any explanation of why it doesn't work for non-powers of 2, so I'm...
View ArticleAnswer by Dr.jacky for How to check if a number is a power of 2
Kotlin:fun isPowerOfTwo(n: Int): Boolean { return (n > 0) && (n.and(n-1) == 0)}orfun isPowerOfTwo(n: Int): Boolean { if (n == 0) return false return (n and (n - 1).inv()) == n}inv inverts...
View ArticleAnswer by velocity for How to check if a number is a power of 2
I've been reading the documentation for Random.nextInt(int bound) and saw this nice piece of code which checks whether the parameter is a power of 2, which says (part of the code) :if ((bound &...
View ArticleAnswer by Cato for How to check if a number is a power of 2
I'm assuming 1 is a power of two, which it is, it's 2 to the power of zero bool IsPowerOfTwo(ulong testValue) { ulong bitTest = 1; while (bitTest != 0) { if (bitTest == testValue) return true; bitTest...
View ArticleAnswer by Rushil Patel for How to check if a number is a power of 2
unsigned int n; // we want to see if n is a power of 2bool f; // the result goes here f = (n & (n - 1)) == 0;Note that 0 is considered a power of 2 here. To remedy this, use:f = n && !(n...
View ArticleAnswer by RARE Kpop Manifesto for How to check if a number is a power of 2
Here's a clean approach if you want to avoid using any and all bitwise ops (this is generic pseudo-code instead of being exactly C#) :func is_power_of_2( uint64 n ) { return (n > 4) ? 2**63 % n == 0...
View ArticleAnswer by Hans Brende for How to check if a number is a power of 2
Many answers solve this cleverly for integers, but here's how, using only basic floating-point operations, to solve it for double!const double HALF_EPS = 1.1102230246251565e-16; // 2^-53bool...
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