# 645. Set Mismatch

• Time: $O(n)$
• Space: $O(1)$
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 class Solution { public: vector findErrorNums(vector& nums) { int duplicate; for (const int num : nums) if (nums[abs(num) - 1] < 0) duplicate = abs(num); else nums[abs(num) - 1] *= -1; for (int i = 0; i < nums.size(); ++i) if (nums[i] > 0) return {duplicate, i + 1}; throw; } }; 
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 class Solution { public int[] findErrorNums(int[] nums) { int duplicate = 0; for (final int num : nums) { if (nums[Math.abs(num) - 1] < 0) duplicate = Math.abs(num); else nums[Math.abs(num) - 1] *= -1; } for (int i = 0; i < nums.length; ++i) if (nums[i] > 0) return new int[] {duplicate, i + 1}; throw new IllegalArgumentException(); } } 
  1 2 3 4 5 6 7 8 9 10 11 class Solution: def findErrorNums(self, nums: List[int]) -> List[int]: for num in nums: if nums[abs(num) - 1] < 0: duplicate = abs(num) else: nums[abs(num) - 1] *= -1 for i, num in enumerate(nums): if num > 0: return [duplicate, i + 1]