leetcode-First Missing Positive

Put each number in its right place.

For example:

When we find 5, then swap it with A[4].

At last, the first place where its number is not right, return the place + 1.

 1 class Solution {
 2 public:
 3     int firstMissingPositive(vector<int>& nums) {
 4         for (int i = 0; i < nums.size(); i++)
 5         {
 6             while (nums[i] > 0 && nums[i] <= nums.size() && nums[i] != nums[nums[i] -1])
 7             {
 8                 swap(nums[i], nums[nums[i] -1]);
 9             }
10         }
11         for (int i = 0; i < nums.size(); i++)
12         {
13             if (nums[i] != i + 1)
14             {
15                 return i + 1;
16             }
17         }
18         return nums.size() + 1;
19     }
20 };