Even occurring elements

PROBLEM :

Given an array that contains odd number of occurrences for all numbers except for a few elements which are present even number of times. Find the elements which have even occurrences in the array in O(n) time complexity and O(1) extra space.

Note: In some array, array contains only odd number then you have to print only a blank new line.

Input:
The first line of input contains a single integer T denoting the number of test cases. Then T test cases follow. Each test case consist of two lines. The first line of each test case consists of an integer N, where N is the size of array.
The second line of each test case contains N space separated integers denoting array elements.

Output:

Corresponding to each test case, in a new line, print the elements which have even occurrences in the array.

Constraints:

1 = T = 100
1 = N = 200
1 = A[i] = 63

Example:

Input
3
11
9 12 23 10 12 12 15 23 14 12 15
5
23 12 56 34 32
4
10 34 10 56

Output
12 23 15

10

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SIMPLE c++ IMPLEMENTATION :
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#include<iostream>
using namespace std;
int main()
 {
int t,no,arr[200],i ;
cin>>t ;
while(t--)
{
   cin>>no ;
   for(i=0;i<no;i++)
       cin>>arr[i] ;
     
   int hash[64]={0} ;
 
   for(i=0;i<no;i++)
       hash[arr[i]]++ ;
     
   for(i=0;i<no;i++)
   {
       if(hash[arr[i]]%2==0)
       {
           cout<<arr[i]<<" " ;
           hash[arr[i]]=-1 ;
       }
   }
   cout<<endl ;
}
return 0;
}

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