class Solution {

public:

    int firstMissingPositive(vector<int>& nums) {

        //从1开始将范围内的整数交换到对应的位置

        int len=nums.size();

        int res=;

        for(int i=;i<len;i++){

            int x=i;

            /*//show every state before swap

            cout<<"nums["<<i<<"]: "<<endl;

            for(int j=0;j<len;j++)

                cout<<nums[j]<<",";

                cout<<endl;*/

            while(nums[x]> && nums[x]<len && nums[x]!=nums[nums[x]-]){

                swap(nums[x],nums[nums[x]-]);

                /*//show every swap result

                for(int j=0;j<len;j++)

                    cout<<nums[j]<<",";

                cout<<endl;*/

            }

        }

        for(int i=;i<len;i++){

            if(nums[i]!=i+) break;

            res++;

        }

        return res;

    }

};