Return node where the loop starts
"""
# Approach: Add nodes to hash table. If a node already exists in table,
# then loop begins at that node--O(n)
nodeSet = set()
curNode = circularSLL.head
while curNode != None:
if curNode in nodeSet:
return curNode
else:
nodeSet.add(curNode)
curNode = curNode.next
return None
# Test cases
n2 = Node('B')
n3 = Node('C')
n4 = Node('D')
n5 = Node('E')
sll = createSinglyLinkedList('A')
appendToSinglyLinkedList(sll, n2)
appendToSinglyLinkedList(sll, n3)
appendToSinglyLinkedList(sll, n4)
appendToSinglyLinkedList(sll, n5)
appendToSinglyLinkedList(sll, n3) # Loop here. Ans: 'C' (n3)
print(loopDetection(sll))
while curNode != None:
# If already in set, then the 2 lists intersect at curNode
if curNode in nodeSet:
return curNode
else:
nodeSet.add(curNode)
curNode = curNode.next
# No intersection
return None
# Test cases
a1, a2 = [1, 2, 3], [4, 5]
# Create singly linked lists for testing
sll1 = createSinglyLinkedList(a1)
sll2 = createSinglyLinkedList(a2)
# Intersecting case: Add common node(s) to both lists. Ans: 100
n = Node(100)
# Non-intersecting case Ans: None
appendToSinglyLinkedList(sll1, n)
appendToSinglyLinkedList(sll2, n)
res = intersection(sll1, sll2)
if res != None:
print(sll1, "and", sll2, "intersect at", res)
else:
print("No intersection")