def test_child_methods(self):
# Create node 'A' and verify it does not have any children
node_A = PrefixTreeNode('A')
assert node_A.num_children() == 0
assert node_A.has_child('B') is False
# Verify getting child from node 'A' raises error
with self.assertRaises(ValueError):
node_A.get_child('B')
# Create node 'B' and add it as child to node 'A'
node_B = PrefixTreeNode('B')
node_A.add_child('B', node_B)
# Verify node 'A' has node 'B' as child
assert node_A.num_children() == 1
assert node_A.has_child('B') is True
assert node_A.get_child('B') is node_B
# Verify adding node 'B' as child to node 'A' again raises error
with self.assertRaises(ValueError):
node_A.add_child('B', node_B)
# Create node 'C' and add it as another child to node 'A'
node_C = PrefixTreeNode('C')
node_A.add_child('C', node_C)
# Verify node 'A' has both nodes 'B' and 'C' as children
assert node_A.num_children() == 2
assert node_A.has_child('B') is True
assert node_A.has_child('C') is True
assert node_A.get_child('C') is node_C
# Verify adding node 'C' as child to node 'A' again raises error
with self.assertRaises(ValueError):
node_A.add_child('C', node_C)
def _traverse(self, node: PrefixTreeNode, prefix: str,
visit: Callable) -> None:
"""Traverse this prefix tree with recursive depth-first traversal.
Start at the given node with the given prefix representing its path in
this prefix tree and visit each node with the given visit function."""
# Once the node is filled with characters and contains a terminal node, it'll append
if node.is_terminal():
visit(prefix)
for char in node.children.keys():
next_node = node.get_child(char)
self._traverse(next_node, prefix + char, visit)
