Find One’s Complement of an Integer

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++

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// 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;
} 

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Java














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// 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. 



















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Python3














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# 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. 



















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C#














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// 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. 



















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PHP














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<?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 


?>  



















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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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