挺简单的困难题

class Solution {
public:int firstMissingPositive(vector<int>& nums) {sort(nums.begin(),nums.end());int n=nums.size();int i=0;bool b=0;if(nums[0]>=0) b=1;int p=1;for(;i<n;i++){if(i+1>0&&i+1<nums.size()&&nums[i]<=0&&nums[i+1]>0){nums.erase(nums.begin(),nums.begin()+i+1);i=0;n=nums.size();b=1;}if(b==1&&nums[i]!=p&&nums[i]!=p-1) {return p;}else if(b==1&&nums[i]==p) p++;}return p;}
};