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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. int main() {
  5.     int n; //number of elements
  6.  
  7.     cout << "Enter the number of elements : ";
  8.     cin >> n;
  9.  
  10.     //Declaring array
  11.     int arr[n-1];
  12.  
  13.     //Taking input
  14.     for(int i = 0; i<n-1; i++)
  15.     cin >> arr[i];
  16.  
  17.     //printing array
  18.     cout << "\nElements are :";
  19.     for(int i = 0; i<n-1; i++)
  20.     cout << " " << arr[i];
  21.  
  22.     //Declaring elements to take XOR
  23.     int x1 = arr[0]; // first element of array
  24.     int x2 = 1; //first element in natural number series i.e 1,2,3,4...
  25.  
  26.     //taking XOR of all elements of the given array
  27.     for(int i = 1; i<n-1; i++)
  28.     x1 ^= arr[i];
  29.  
  30.     //taking XOR of all the natural numbers till 'n'
  31.     for(int i = 2; i<arr[n-1]; i++)
  32.     x2 ^= i;
  33.  
  34.     //Finally printing the output by taking XOR of x1 and x2
  35.     //because same numbers will be removed since (A^A) = 0 also (A^0) = A
  36.     cout << "\nMissing number : " << (x1^x2) << endl;
  37.     return 0;
  38. }
Success #stdin #stdout 0.66s 15232KB
comments (?)
stdin 
9
1 2 3 4 5 7 8 9
stdout 
Enter the number of elements : 
Elements are : 1 2 3 4 5 7 8 9
Missing number : 7
https://ideone.com/gAeFzF
language:
C++ (gcc 8.3)
created:
7 years ago
visibility:
public

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