"""

To find the single element in an array that appears only once. All the other elements appear TWICE.

Contraints : TC - Linear SC - O(1)

"""

int findUnique(int arr[])

{

if(arr.length() == 1) // Corner case

return arr[0];

int res = arr[0] ^ arr[1];

for(int i = 2 ; i < arr.length(); i++)

res ^= arr[i]; // bitwise XOR with all the elements

return res;

}

"""

So a number when XORed with itself, gives 0. And XOR is commutative.

So XORing all the elements together, will cancel out the pairs and leave the unique element.

"""