leetcode:First Missing Positive

class Solution {public:    int firstMissingPositive(int A[], int n) {        for(int i =0 ;i < n;i++)        {            if(A[i]<=n && A[i] > 0)            {                int temp = A[i];                if(A[i] != A[temp-1])                {                    A[i] = A[temp-1];                    A[temp-1] = temp;                    i--;                }            }        }        int result = 1;        for(int i =0 ; i < n;i++)        {            if(A[i] != result)                return result;            result++;        }        return result;    }};