Single Number - LeetCode

Given a non-empty array of integers, every element appears twice except for one. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Example 1:

Input: [2,2,1]
Output: 1

Example 2:

Input: [4,1,2,1,2]
Output: 4

Java Solution: Using HashSet

class Solution {
    public int singleNumber(int[] nums) {
        HashSet<Integer> set = new HashSet<Integer>();
        for(int i : nums)
        {
            if(!set.add(i))
                set.remove(i);
        }
        Iterator<Integer> it = set.iterator();
        return it.next();
        
    }
}

Java Solution : Using XOR Operation

class Solution {
    public int singleNumber(int[] nums) {
        Arrays.sort(nums);
        int x =0;
        for(int n : nums){
            x = x ^ n;
        }
        return x;
    }
}