【LeetCode热题100】【数组】缺失的第一个正数

class Solution {
public:
    int firstMissingPositive(vector<int> &nums) {
        int n = nums.size();
        for (int i = 0; i < n; ++i) {
            while (nums[i] > 0 && nums[i] <= n && nums[i] != nums[nums[i] - 1])
                swap(nums[i], nums[nums[i] - 1]);
        }
        for (int i = 0; i < n; ++i)
            if (nums[i] != i + 1)
                return i + 1;
        return n + 1;
    }
};