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Find One’s Complement of an Integer
  • Difficulty Level : Medium
  • Last Updated : 09 Nov, 2020

Given an integer n, find the one’s complement of the integer.

Examples:

Input  : n = 5
Output : 2

Input  : n = 255
Output : 0

Input  : n = 26
Output : 5

An efficient approach to this problem is as follows:
1. Find the number of bits in the given integer
2. XOR the given integer with 2^number_of_bits-1

C++




// CPP program to find 1's complement of n.
#include<bits/stdc++.h>
using namespace std;
  
unsigned int onesComplement(unsigned int n)
{
   // Find number of bits in the given integer
   int number_of_bits = floor(log2(n))+1;
  
   // XOR the given integer with poe(2, 
   // number_of_bits-1 and print the result 
   return ((1 << number_of_bits) - 1) ^ n;
}
  
int main()
{
  unsigned int n = 22;
  cout << onesComplement(n);
  return 0;


Java




// Java program to find 1's complement of n.
class GFG {
      
    static int onesComplement(int n)
    {
          
        // Find number of bits in the 
        // given integer
        int number_of_bits = 
               (int)(Math.floor(Math.log(n) /
                             Math.log(2))) + 1;
  
        // XOR the given integer with poe(2,
        // number_of_bits-1 and print the result
        return ((1 << number_of_bits) - 1) ^ n;
    }
      
    // Driver code
    public static void main(String[] args)
    {
        int n = 22;
          
        System.out.print(onesComplement(n));
    }
}
  
// This code is contributed by Anant Agarwal.


Python3




# Python3 program to find
# 1's complement of n.
import math
  
def onesComplement(n):
  
    # Find number of bits in
    # the given integer
    number_of_bits = (int)(math.floor(math.log(n) /
                                math.log(2))) + 1;
  
    # XOR the given integer with poe(2, 
    # number_of_bits-1 and print the result 
    return ((1 << number_of_bits) - 1) ^ n;
  
# Driver code
n = 22
print(onesComplement(n))
  
# This code is contributed by Anant Agarwal.


C#




// C# program to find 1's complement of n.
using System;
  
class GFG {
      
    static int onesComplement(int n)
    {
          
       // Find number of bits in the given integer
       int number_of_bits = (int)(Math.Floor(
                   Math.Log(n) / Math.Log(2))) + 1;
       
       // XOR the given integer with poe(2, 
       // number_of_bits-1 and print the result 
       return ((1 << number_of_bits) - 1) ^ n;
    }
      
    //Driver code
    public static void Main ()
    {
          
        int n = 22;
          
        Console.WriteLine(onesComplement(n));
    }
}
  
// This code is contributed by Anant Agarwal.


PHP




<?php
// PHP program to find 1's
// complement of n.
  
function Log2($x)
    return (log10($x) / log10(2));
}
  
function onesComplement($n)
{
      
// Find number of bits in 
// the given integer
$number_of_bits = floor(log2($n)) + 1;
  
// XOR the given integer with 
// number_of_bits-1 and print the result 
return ((1 << $number_of_bits) - 1) ^ $n;
}
  
// Driver Code
$n = 22;
echo onesComplement($n);
  
// This code is contributed by ihritik
?> 



Output :



9


This article is contributed by Amit S K. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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