1class Solution {2    public int firstMissingPositive(int[] nums) {3        int n = nums.length;4        for (int i = 0; i < n; i++) {5            while (nums[i] >= 1 && nums[i] <= n && nums[nums[i] - 1] != nums[i]) {6                int destination = nums[i] - 1;7                int temp = nums[destination];8                nums[destination] = nums[i];9                nums[i] = temp;10            }11        }12        for (int i = 0; i < n; i++) {13            if (nums[i] != i + 1) return i + 1;14        }15        return n + 1;16    }17}