Given an unsorted integer array, find the first missing positive integer.

For example,

Given [1,2,0] return 3,

and [3,4,-1,1] return 2.

Your algorithm should run in O(n) time and uses constant space.

class Solution {public:    int firstMissingPositive(int A[], int n) {        int i,j;        for(i=0;i
     
      n)continue;            swap(A[i],A[cur-1]);            if(A[i]!=A[cur-1])                i--;        }        for(i=0;i