Given an integer n, find whether it is a power of 4 or not.
Example :
Input : 16 Output : 16 is a power of 4 Input : 20 Output : 20 is not a power of 4
We strongly recommend that you click here and practice it, before moving on to the solution.
1. A simple method is to take log of the given number on base 4, and if we get an integer then number is power of 4.
2. Another solution is to keep dividing the number by 4, i.e, do n = n/4 iteratively. In any iteration, if n%4 becomes non-zero and n is not 1 then n is not a power of 4, otherwise n is a power of 4.
C
#include<stdio.h>
#define bool int
/* Function to check if x is power of 4*/
bool isPowerOfFour(int n)
{
if(n == 0)
return 0;
while(n != 1)
{
if(n % 4 != 0)
return 0;
n = n / 4;
}
return 1;
}
/*Driver program to test above function*/
int main()
{
int test_no = 64;
if(isPowerOfFour(test_no))
printf("%d is a power of 4", test_no);
else
printf("%d is not a power of 4", test_no);
getchar();
}
Java
// Java code to check if given
// number is power of 4 or not
class GFG {
// Function to check if
// x is power of 4
static int isPowerOfFour(int n)
{
if(n == 0)
return 0;
while(n != 1)
{
if(n % 4 != 0)
return 0;
n = n / 4;
}
return 1;
}
// Driver program
public static void main(String[] args)
{
int test_no = 64;
if(isPowerOfFour(test_no) == 1)
System.out.println(test_no +
" is a power of 4");
else
System.out.println(test_no +
"is not a power of 4");
}
}
// This code is contributed
// by prerna saini
Python3
# Python3 program to check if given
# number is power of 4 or not
# Function to check if x is power of 4
def isPowerOfFour(n):
if (n == 0):
return False
while (n != 1):
if (n % 4 != 0):
return False
n = n // 4
return True
# Driver code
test_no = 64
if(isPowerOfFour(64)):
print(test_no, 'is a power of 4')
else:
print(test_no, 'is not a power of 4')
# This code is contributed by Danish Raza
C#
// C# code to check if given
// number is power of 4 or not
using System;
class GFG {
// Function to check if
// x is power of 4
static int isPowerOfFour(int n)
{
if (n == 0)
return 0;
while (n != 1) {
if (n % 4 != 0)
return 0;
n = n / 4;
}
return 1;
}
// Driver code
public static void Main()
{
int test_no = 64;
if (isPowerOfFour(test_no) == 1)
Console.Write(test_no +
" is a power of 4");
else
Console.Write(test_no +
" is not a power of 4");
}
}
// This code is contributed by Sam007
PHP
<?php
// PHP code to check if given
// number is power of 4 or not
// Function to check if
// x is power of 4
function isPowerOfFour($n)
{
if($n == 0)
return 0;
while($n != 1)
{
if($n % 4 != 0)
return 0;
$n = $n / 4;
}
return 1;
}
// Driver Code
$test_no = 64;
if(isPowerOfFour($test_no))
echo $test_no," is a power of 4";
else
echo $test_no," is not a power of 4";
// This code is contributed by Rajesh
?>
Output :
64 is a power of 4
3. A number n is a power of 4 if following conditions are met.
a) There is only one bit set in the binary representation of n (or n is a power of 2)
b) The count of zero bits before the (only) set bit is even.
For example: 16 (10000) is power of 4 because there is only one bit set and count of 0s before the set bit is 4 which is even.
Thanks to Geek4u for suggesting the approach and providing the code.
C
#include<stdio.h>
#define bool int
bool isPowerOfFour(unsigned int n)
{
int count = 0;
/*Check if there is only one bit set in n*/
if ( n && !(n&(n-1)) )
{
/* count 0 bits before set bit */
while(n > 1)
{
n >>= 1;
count += 1;
}
/*If count is even then return true else false*/
return (count%2 == 0)? 1 :0;
}
/* If there are more than 1 bit set
then n is not a power of 4*/
return 0;
}
/*Driver program to test above function*/
int main()
{
int test_no = 64;
if(isPowerOfFour(test_no))
printf("%d is a power of 4", test_no);
else
printf("%d is not a power of 4", test_no);
getchar();
}
Java
// Java program to check
// if given number is
// power of 4 or not
import java.io.*;
class GFG
{
static int isPowerOfFour(int n)
{
int count = 0;
/*Check if there is
only one bit set in n*/
int x = n & (n - 1);
if ( n > 0 && x == 0)
{
/* count 0 bits
before set bit */
while(n > 1)
{
n >>= 1;
count += 1;
}
/*If count is even
then return true
else false*/
return (count % 2 == 0) ? 1 : 0;
}
/* If there are more than
1 bit set then n is not a
power of 4*/
return 0;
}
// Driver Code
public static void main(String[] args)
{
int test_no = 64;
if(isPowerOfFour(test_no)>0)
System.out.println(test_no +
" is a power of 4");
else
System.out.println(test_no +
" is not a power of 4");
}
}
// This code is contributed by mits
Python3
# Python3 program to check if given
# number is power of 4 or not
# Function to check if x is power of 4
def isPowerOfFour(n):
count = 0
# Check if there is only one
# bit set in n
if (n and (not(n & (n - 1)))):
# count 0 bits before set bit
while(n > 1):
n >>= 1
count += 1
# If count is even then return
# true else false
if(count % 2 == 0):
return True
else:
return False
# Driver code
test_no = 64
if(isPowerOfFour(64)):
print(test_no, 'is a power of 4')
else:
print(test_no, 'is not a power of 4')
# This code is contribued by Danish Raza
C#
// C# program to check if given
// number is power of 4 or not
using System;
class GFG {
static int isPowerOfFour(int n)
{
int count = 0;
/*Check if there is only one bit
set in n*/
int x = n & (n-1);
if ( n > 0 && x == 0)
{
/* count 0 bits before set bit */
while(n > 1)
{
n >>= 1;
count += 1;
}
/*If count is even then return
true else false*/
return (count % 2 == 0) ? 1 : 0;
}
/* If there are more than 1 bit set
then n is not a power of 4*/
return 0;
}
/*Driver program to test above function*/
static void Main()
{
int test_no = 64;
if(isPowerOfFour(test_no)>0)
Console.WriteLine("{0} is a power of 4",
test_no);
else
Console.WriteLine("{0} is not a power of 4",
test_no);
}
}
// This Code is Contributed by mits
PHP
<?php
function isPowerOfFour($n)
{
$count = 0;
/*Check if there is only one bit set in n*/
if ( $n && !($n&($n-1)) )
{
/* count 0 bits before set bit */
while($n > 1)
{
$n >>= 1;
$count += 1;
}
/*If count is even then return true else false*/
return ($count%2 == 0)? 1 :0;
}
/* If there are more than 1 bit set
then n is not a power of 4*/
return 0;
}
/*Driver program to test above function*/
$test_no = 64;
if(isPowerOfFour($test_no))
echo $test_no, " is a power of 4";
else
echo $test_no, " not is a power of 4";
#This Code is Contributed by Ajit
?>
Output:
64 is a power of 4
Please write comments if you find any of the above codes/algorithms incorrect, or find other ways to solve the same problem.
Practice Tags :
Recommended Posts:
- Compute modulus division by a power-of-2-number
- Compute the integer absolute value (abs) without branching
- Turn off the rightmost set bit
- Rotate bits of a number
- Program to find whether a no is power of two
- Sum of the series 2^0 + 2^1 + 2^2 +…..+ 2^n
- Print all the combinations of N elements by changing sign such that their sum is divisible by M
- String transformation using XOR and OR
- Check if a number has same number of set and unset bits
- Sum of all elements up to Nth row in a Pascal triangle
Writing code in comment? Please use ide.geeksforgeeks.org, generate link and share the link here.