LeetCode268

class Solution { public int missingNumber(int[] nums) { Arrays.sort(nums); int n = nums.length; if(nums[n-1] != n){ return n; } if(nums[0]!=0){ return 0; } for(int i = 1;i<n;i++){ int m = nums[i-1]+1; if(m != nums[i]){ return m; } } return -1; } }