Unpaired element in array

I started using codility after long, and turned to a very basic problem. It was easy and did not take me more than 10 minutes to solve. I worked out the testcases by hand, and then was browsing a bit on Java basics after I finished the code, then submitted it. Otherwise it was so easy that I doubt the possibility of this occurring on any interview.

Still I felt that it was beneficial to solve it because:

>> It helped me jargon bitwise operators in mind ensuring I wouldn't mistake the syntaxes due to rustiness (we bearly use bitwise in day-to-day job, do we?)

>> It gave me a confidence boost to crack the best solution with perfect testcases / edge cases in one go.

Problem:

A non-empty zero-indexed array A consisting of N integers is given. The array contains an odd number of elements, and each element of the array can be paired with another element that has the same value, except for one element that is left unpaired.

For example, in array A such that:

  A[0] = 9  A[1] = 3  A[2] = 9
  A[3] = 3  A[4] = 9  A[5] = 7
  A[6] = 9

• the elements at indexes 0 and 2 have value 9,
• the elements at indexes 1 and 3 have value 3,
• the elements at indexes 4 and 6 have value 9,
• the element at index 5 has value 7 and is unpaired.

Write a function:

class Solution { public int solution(int[] A); }

that, given an array A consisting of N integers fulfilling the above conditions, returns the value of the unpaired element.

For example, given array A such that:

  A[0] = 9  A[1] = 3  A[2] = 9
  A[3] = 3  A[4] = 9  A[5] = 7
  A[6] = 9

the function should return 7, as explained in the example above.

Assume that:

• N is an odd integer within the range [1..1,000,000];
• each element of array A is an integer within the range [1..1,000,000,000];
• all but one of the values in A occur an even number of times.

Complexity:

• expected worst-case time complexity is O(N);
• expected worst-case space complexity is O(1), beyond input storage (not counting the storage required for input arguments).

Elements of input arrays can be modified.

My solution that received 100%

class Solution { public int solution(int[] A) { int temp = 0; for(int i = 0; i < A.length; i++) { temp = temp ^ A[i]; } return temp; } }