Day 10.1.txt

1539. Kth Missing Positive Number

Given an array arr of positive integers sorted in a strictly increasing order, and an integer k.

Find the kth positive integer that is missing from this array.

 

Example 1:

Input: arr = [2,3,4,7,11], k = 5
Output: 9
Explanation: The missing positive integers are [1,5,6,8,9,10,12,13,...]. The 5th missing positive integer is 9.
Example 2:

Input: arr = [1,2,3,4], k = 2
Output: 6
Explanation: The missing positive integers are [5,6,7,...]. The 2nd missing positive integer is 6.
 

Constraints:

1 <= arr.length <= 1000
1 <= arr[i] <= 1000
1 <= k <= 1000
arr[i] < arr[j] for 1 <= i < j <= arr.length


class Solution {
    public int findKthPositive(int[] a, int k) {
        ArrayList<Integer> nm=new ArrayList<>();
        int i,j=1;
        for(i=0;i<a.length;j++)
        {
            if(j!=a[i])
            {
                nm.add(j);
                if(nm.size()==k)
                    break;
            }
            else
                i++;
        }
        if(i==a.length&&nm.size()==0)
        {
            return a[i-1]+k;
        }
        else if(nm.size()==k)
            return nm.get(k-1);
        else
        {
            return j+(k-nm.size()-1);
        }
    }
}