def test_expression_tree_populate_lookup_doctest() -> None:
"""Test ExprTree.populate_lookup on the provided doctest"""
expr_t = ExprTree('a', [])
look_up = {}
expr_t.populate_lookup(look_up)
assert look_up['a'] == 0
assert len(look_up) == 1
def test_expression_tree_eval_doctest() -> None:
"""Test ExprTree.eval on the provided doctest"""
exp_t = ExprTree('+', [ExprTree(3, []),
ExprTree('*', [ExprTree('x', []),
ExprTree('y', [])]),
ExprTree('x', [])])
look_up = {}
exp_t.populate_lookup(look_up)
assert exp_t.eval(look_up) == 3
look_up['x'] = 7
look_up['y'] = 3
assert exp_t.eval(look_up) == 31
def __init__(self, tree: ExprTree, target: int) -> None:
"""
Create a new expression tree puzzle given the provided
expression tree and the target value. The variables are initialized
using the tree's populate_lookup method.
>>> puz = ExpressionTreePuzzle(ExprTree('a', []), 4)
>>> puz.variables == {'a': 0}
True
>>> puz.target
4
"""
self.variables = {}
tree.populate_lookup(self.variables)
self._tree = tree
self.target = target
