first-missing-positive

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