Solve two linked list/array tasks

You are given two independent coding tasks.

Task 1: Remove the N-th node from the end of a singly linked list

Given the head of a singly linked list and an integer n, remove the n-th node from the end of the list and return the head of the modified list.

Input

• head : head node of a singly linked list (node has fields val and next )
• n : integer

Output

• The head of the list after removal

Constraints (typical interview assumptions)

• 1 <= n <= length(list)
• List length can be up to 10^5

Example

• List: 1 -> 2 -> 3 -> 4 -> 5 , n = 2
• Result: 1 -> 2 -> 3 -> 5

Task 2: Find the k-th missing positive number from a strictly increasing array

You are given a strictly increasing array arr of positive integers and an integer k. Consider the infinite sequence of positive integers 1, 2, 3, .... Return the k-th positive integer that is missing from arr.

Input

• arr : strictly increasing array of positive integers
• k : positive integer

Output

• The k-th missing positive number

Constraints (typical interview assumptions)

• 1 <= arr.length <= 10^5
• 1 <= arr[i] <= 10^9
• 1 <= k <= 10^9

Example

• arr = [2, 3, 4, 7, 11] , k = 5
• Missing positives are [1, 5, 6, 8, 9, 10, ...] → answer is 9