class Solution {
public:
    int firstMissingPositive(vector<int>& nums)
    {    
        int n = nums.size();
        int ans = n + 1;
        vector<int> l(n + 1, 0);

        for (int i = 0; i < n; i++) {
            if (nums[i] <= 0 || nums[i] > n)
                l[n] = 1;
            else
                l[nums[i] - 1] = 1;
        }

        for (int i = 0; i < n; i++) {
            if (l[i] == 0) {
                ans = i + 1;
                break;
            }
        }

        return ans;
    }
};