Nth Node from End

Problem

Return the value of the n-th node from the end of a singly linked list.

n is 1-based, so n = 1 is the last node. Use the two-pointer trick: advance a lead pointer n steps, then move both pointers until the lead reaches the end.

Return None when n is out of range.

Hint

The n-th node from the end sits at index length - n.

Test cases

case 1

in: [[1,2,3,4,5],2]

expected: 4

case 2

in: [[1],1]

expected: 1

case 3

in: [[1,2],3]

expected: null

case 4

in: [[],1]

expected: null

Starter codePython

def nth_from_end(values, n):
    # Your code here
    pass

4 test cases · run your code against them in the editor