一:题目

二:上码

class Solution {public int singleNumber(int[] nums) {int ans = -100;Arrays.sort(nums);for (int i = 0; i < nums.length-1; i+=2) {if (nums[i] != nums [i+1]) {ans = nums[i];break;}}return ans == -100 ? nums[nums.length-1] : ans;}
}