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Add is_symmetric property #20

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Merged
merged 1 commit into from
Jul 19, 2019
Merged

Add is_symmetric property #20

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60 changes: 59 additions & 1 deletion binarytree/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,27 @@ def _is_bst(root, min_value=float('-inf'), max_value=float('inf')):
)


def _is_symmetric(root):
"""Check if the binary tree is symmetric

:param root: Root node of the binary tree
:type root: binarytree.Node | None
:return: True if the binary tree is symmetric, False otherwise.
:rtype: bool
"""
def symmetric_helper(left_subtree, right_subtree):
if left_subtree is None and right_subtree is None:
return True
if left_subtree is None or right_subtree is None:
return False
return (
left_subtree.value == right_subtree.value and
symmetric_helper(left_subtree.left, right_subtree.right) and
symmetric_helper(left_subtree.right, right_subtree.left)
)
return symmetric_helper(root, root)


def _validate_tree_height(height):
"""Check if the height of the binary tree is valid.

Expand Down Expand Up @@ -1103,6 +1124,40 @@ def is_bst(self):
"""
return _is_bst(self, float('-inf'), float('inf'))

@property
def is_symmetric(self):
"""Check if the binary tree is symmetric.

* Left subtree is a mirror of the right subtree around the center

:return: True if the binary tree is a symmetric, False otherwise.
:rtype: bool

**Example**:

.. doctest::

>>> from binarytree import Node
>>> root = Node(1)
>>> root.left = Node(2)
>>> root.right = Node(2)
>>> root.left.left = Node(3)
>>> root.left.right = Node(4)
>>> root.right.left = Node(4)
>>> root.right.right = Node(3)
>>> print(root)
<BLANKLINE>
__1__
/ \\
2 2
/ \\ / \\
3 4 4 3
<BLANKLINE>
>>> root.is_symmetric
True
"""
return _is_symmetric(self)

@property
def is_max_heap(self):
"""Check if the binary tree is a `max heap`_.
Expand Down Expand Up @@ -1424,6 +1479,8 @@ def properties(self):
False
>>> props['is_complete'] # equivalent to root.is_complete
True
>>> props['is_symmetric'] # equivalent to root.is_symmetric
False
>>> props['is_max_heap'] # equivalent to root.is_max_heap
False
>>> props['is_min_heap'] # equivalent to root.is_min_heap
Expand All @@ -1436,7 +1493,8 @@ def properties(self):
properties = _get_tree_properties(self)
properties.update({
'is_bst': _is_bst(self),
'is_balanced': _is_balanced(self) >= 0
'is_balanced': _is_balanced(self) >= 0,
'is_symmetric': _is_symmetric(self)
})
return properties

Expand Down
15 changes: 15 additions & 0 deletions tests/test_tree.py
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Original file line number Diff line number Diff line change
Expand Up @@ -414,6 +414,7 @@ def test_tree_properties():
'is_min_heap': True,
'is_perfect': True,
'is_strict': True,
'is_symmetric': True,
'leaf_count': 1,
'max_leaf_depth': 0,
'max_node_value': 1,
Expand All @@ -429,6 +430,7 @@ def test_tree_properties():
assert root.is_min_heap is True
assert root.is_perfect is True
assert root.is_strict is True
assert root.is_symmetric is True
assert root.leaf_count == 1
assert root.max_leaf_depth == 0
assert root.max_node_value == 1
Expand All @@ -446,6 +448,7 @@ def test_tree_properties():
'is_min_heap': True,
'is_perfect': False,
'is_strict': False,
'is_symmetric': False,
'leaf_count': 1,
'max_leaf_depth': 1,
'max_node_value': 2,
Expand All @@ -461,6 +464,7 @@ def test_tree_properties():
assert root.is_min_heap is True
assert root.is_perfect is False
assert root.is_strict is False
assert root.is_symmetric is False
assert root.leaf_count == 1
assert root.max_leaf_depth == 1
assert root.max_node_value == 2
Expand All @@ -478,6 +482,7 @@ def test_tree_properties():
'is_min_heap': True,
'is_perfect': True,
'is_strict': True,
'is_symmetric': False,
'leaf_count': 2,
'max_leaf_depth': 1,
'max_node_value': 3,
Expand All @@ -493,6 +498,7 @@ def test_tree_properties():
assert root.is_min_heap is True
assert root.is_perfect is True
assert root.is_strict is True
assert root.is_symmetric is False
assert root.leaf_count == 2
assert root.max_leaf_depth == 1
assert root.max_node_value == 3
Expand All @@ -510,6 +516,7 @@ def test_tree_properties():
'is_min_heap': True,
'is_perfect': False,
'is_strict': False,
'is_symmetric': False,
'leaf_count': 2,
'max_leaf_depth': 2,
'max_node_value': 4,
Expand All @@ -525,6 +532,7 @@ def test_tree_properties():
assert root.is_min_heap is True
assert root.is_perfect is False
assert root.is_strict is False
assert root.is_symmetric is False
assert root.leaf_count == 2
assert root.max_leaf_depth == 2
assert root.max_node_value == 4
Expand All @@ -542,6 +550,7 @@ def test_tree_properties():
'is_min_heap': False,
'is_perfect': False,
'is_strict': False,
'is_symmetric': False,
'leaf_count': 2,
'max_leaf_depth': 2,
'max_node_value': 5,
Expand All @@ -557,6 +566,7 @@ def test_tree_properties():
assert root.is_min_heap is False
assert root.is_perfect is False
assert root.is_strict is False
assert root.is_symmetric is False
assert root.leaf_count == 2
assert root.max_leaf_depth == 2
assert root.max_node_value == 5
Expand All @@ -574,6 +584,7 @@ def test_tree_properties():
'is_min_heap': False,
'is_perfect': False,
'is_strict': False,
'is_symmetric': False,
'leaf_count': 2,
'max_leaf_depth': 3,
'max_node_value': 6,
Expand All @@ -589,6 +600,7 @@ def test_tree_properties():
assert root.is_min_heap is False
assert root.is_perfect is False
assert root.is_strict is False
assert root.is_symmetric is False
assert root.leaf_count == 2
assert root.max_leaf_depth == 3
assert root.max_node_value == 6
Expand All @@ -606,6 +618,7 @@ def test_tree_properties():
'is_min_heap': False,
'is_perfect': False,
'is_strict': False,
'is_symmetric': False,
'leaf_count': 2,
'max_leaf_depth': 3,
'max_node_value': 7,
Expand All @@ -621,6 +634,7 @@ def test_tree_properties():
assert root.is_min_heap is False
assert root.is_perfect is False
assert root.is_strict is False
assert root.is_symmetric is False
assert root.leaf_count == 2
assert root.max_leaf_depth == 3
assert root.max_node_value == 7
Expand Down Expand Up @@ -861,6 +875,7 @@ def test_heap_float_values():
assert root.is_min_heap == root_copy.is_min_heap
assert root.is_perfect == root_copy.is_perfect
assert root.is_strict == root_copy.is_strict
assert root.is_symmetric == root_copy.is_symmetric
assert root.leaf_count == root_copy.leaf_count
assert root.max_leaf_depth == root_copy.max_leaf_depth
assert root.max_node_value == root_copy.max_node_value + 0.1
Expand Down