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Smallest perfect power of 2 greater than n (without using arithmetic operators)
  • Difficulty Level : Hard
  • Last Updated : 05 Mar, 2021

Given a non-negative integer n. The problem is to find the smallest perfect power of 2 which is greater than n without using the arithmetic operators.
Examples : 
 

Input : n = 10
Output : 16

Input : n = 128
Output : 256

 

Algorithm : 
 

 

C++




// C++ implementation of smallest perfect power
// of 2 greater than n
#include <bits/stdc++.h>
 
using namespace std;
 
// Function to find smallest perfect power
// of 2 greater than n
unsigned int perfectPowerOf2(unsigned int n)
{
    // To store perfect power of 2
    unsigned int per_pow = 1;
 
    while (n > 0)
    {
        // bitwise left shift by 1
        per_pow = per_pow << 1;
 
        // bitwise right shift by 1
        n = n >> 1;
    }
 
    // Required perfect power of 2
    return per_pow;
}
 
// Driver program to test above
int main()
{
    unsigned int n = 128;
    cout << "Perfect power of 2 greater than "
        << n << ": " << perfectPowerOf2(n);
    return 0;
}

Java




// JAVA Code for Smallest perfect
// power of 2 greater than n
import java.util.*;
 
class GFG {
     
    // Function to find smallest perfect
    // power of 2 greater than n
    static int perfectPowerOf2( int n)
    {
        // To store perfect power of 2
         int per_pow = 1;
      
        while (n > 0)
        {
            // bitwise left shift by 1
            per_pow = per_pow << 1;
             
            n = n >> 1;
        }
      
        // Required perfect power of 2
        return per_pow;
    }
     
    // Driver program
    public static void main(String[] args)
    {
         int n = 12;
         System.out.println("Perfect power of 2 greater than "
                            + n + ": " + perfectPowerOf2(n));
        }
    }
         
    //This code is contributed by Arnav Kr. Mandal.

Python3




# Python3 implementation of smallest
# perfect power of 2 greater than n
 
# Function to find smallest perfect
# power of 2 greater than n
def perfectPowerOf2( n ):
     
    # To store perfect power of 2
    per_pow = 1
     
    while n > 0:
     
        # bitwise left shift by 1
        per_pow = per_pow << 1
         
        # bitwise right shift by 1
        n = n >> 1
         
    # Required perfect power of 2
    return per_pow
 
# Driver program to test above
n = 128
print("Perfect power of 2 greater than",
            n, ":",perfectPowerOf2(n))
 
# This code is contributed by "Sharad_Bhardwaj".

C#




// C# Code for Smallest perfect
// power of 2 greater than n
using System;
 
class GFG {
 
    // Function to find smallest perfect
    // power of 2 greater than n
    static int perfectPowerOf2(int n)
    {
        // To store perfect power of 2
        int per_pow = 1;
 
        while (n > 0)
        {
            // bitwise left shift by 1
            per_pow = per_pow << 1;
 
            n = n >> 1;
        }
 
        // Required perfect power of 2
        return per_pow;
    }
 
    // Driver program
    public static void Main()
    {
        int n = 128;
        Console.WriteLine("Perfect power of 2 greater than " +
                           n + ": " + perfectPowerOf2(n));
    }
}
 
// This code is contributed by Sam007

PHP




<?php
// php implementation of
// smallest perfect power
// of 2 greater than n
 
// Function to find smallest
// perfect power of 2
// greater than n
function perfectPowerOf2($n)
{
     
    // To store perfect power of 2
    $per_pow = 1;
 
    while ($n > 0)
    {
        // bitwise left shift by 1
        $per_pow = $per_pow << 1;
 
        // bitwise right shift by 1
        $n = $n >> 1;
    }
 
    // Required perfect power of 2
    return $per_pow;
}
 
    // Driver code
    $n = 128;
    echo "Perfect power of 2 greater than ".
          $n . ": ".perfectPowerOf2($n);
 
// This code is contributed by mits
?>

Javascript




<script>
 
// JavaScript implementation of smallest perfect power
// of 2 greater than n
 
// Function to find smallest perfect power
// of 2 greater than n
function perfectPowerOf2(n)
{
    // To store perfect power of 2
    let per_pow = 1;
 
    while (n > 0)
    {
        // bitwise left shift by 1
        per_pow = per_pow << 1;
 
        // bitwise right shift by 1
        n = n >> 1;
    }
 
    // Required perfect power of 2
    return per_pow;
}
 
// Driver program to test above
 
    let n = 128;
    document.write("Perfect power of 2 greater than "
        + n + ": " + perfectPowerOf2(n));
 
 
// This code is contributed by Surbhi Tyagi.
 
</script>

Output: 

Perfect power of 2 greater than 128: 256

Time Complexity: O(num), where num is the number of bits in the binary representation of n.
 




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