Hi, here’s your problem today. This problem was recently asked by Apple:

You are given two singly linked lists. The lists intersect at some node. Find, and return the node. Note: the lists are non-cyclical.

Example:

A = 1 -> 2 -> 3 -> 4
B = 6 -> 3 -> 4 

This should return 3 (you may assume that any nodes with the same value are the same node).

Here is a starting point:

def intersection(a, b):
  # fill this in.

class Node(object):
  def __init__(self, val):
    self.val = val
    self.next = None
  def prettyPrint(self):
    c = self
    while c:
      print c.val,
      c = c.next

a = Node(1)
a.next = Node(2)
a.next.next = Node(3)
a.next.next.next = Node(4)

b = Node(6)
b.next = a.next.next

c = intersection(a, b)
c.prettyPrint()
# 3 4