Single Number

import java.util.HashSet; import java.util.Set; public class SingleNumber { public static void main(String[] args) { SingleNumber singleNumber = new SingleNumber(); int[] nums = {4, 2, 7, 7, 2}; int result = singleNumber.findSingleNumberXor(nums); System.out.println(result); } public int findSingleNumber(int[] nums) { Set<Integer> set = new HashSet<>(); for (int i = 0; i < nums.length; i++) { if (set.contains(nums[i])) { set.remove(nums[i]); } else { set.add(nums[i]); } } return set.iterator().next(); } public int findSingleNumberXor(int[] nums) { int singleNum = 0; for (int num : nums) { singleNum = singleNum ^ num; } return singleNum; } }