def test_sift_down(self):
"""
Sifting down an element swaps it with the larger of its two children,
and continues to sift down that element in its new position and its new
children, until it is in a position where it obeys the heap property.
Hint: This might only require one more line of code, if expressed recursively.
"""
h = MaxHeap()
h._data.append(2)
h._data.append(9)
h._data.append(10)
h._data.append(5)
h._data.append(4)
h._data.append(7)
h._data.append(6)
h._data.append(1)
h._sift_down(0)
self.assertEqual(10, h._data[0])
self.assertEqual(9, h._data[1])
self.assertEqual(7, h._data[2])
self.assertEqual(5, h._data[3])
self.assertEqual(4, h._data[4])
self.assertEqual(2, h._data[5])
self.assertEqual(6, h._data[6])
self.assertEqual(1, h._data[7])
def test_sift_down_one(self):
"""
Sifting down the root of a single-element heap is easy.
Hint: Be naive for now.
"""
h = MaxHeap()
h._data.append(1)
h._sift_down(0)
self.assertEqual(1, h._data[0])
def test_sift_down_three_unstable_left(self):
"""
Sifting down an element in a three-element heap, swaps it with the larger
of its two children.
"""
h = MaxHeap()
h._data.append(1)
h._data.append(10)
h._data.append(5)
# Sifting down the root of this tree swaps it with its left child.
h._sift_down(0)
self.assertEqual(10, h._data[0])
self.assertEqual(1, h._data[1])
self.assertEqual(5, h._data[2])
def test_sift_down_two_unstable(self):
"""
Sifting down an element in a two-element heap, when the element is smaller
than its child swaps the element with its child.
Hint: A little more genuine now. Use your abstractions!
Hint 2: If it obeys the heap property at that index, there's no work to do.
"""
h = MaxHeap()
h._data.append(1)
h._data.append(5)
# Sifting down the root of this tree swaps it with its child.
h._sift_down(0)
self.assertEqual(5, h._data[0])
self.assertEqual(1, h._data[1])
def test_sift_down_three_unstable_right(self):
"""
Sifting down an element in a three-element heap, swaps it with the larger
of its two children.
Hint: Review your handy helper methods. And use them.
"""
h = MaxHeap()
h._data.append(1)
h._data.append(5)
h._data.append(10)
# Sifting down the root of this tree swaps it with its right child.
h._sift_down(0)
self.assertEqual(10, h._data[0])
self.assertEqual(5, h._data[1])
self.assertEqual(1, h._data[2])
def test_sift_down_two_stable(self):
"""
Sifting down an element in a two-element heap, when the element is larger
than its child, is easy.
Hint: Be naive for now.
"""
h = MaxHeap()
h._data.append(5)
h._data.append(1)
# Sifting down the root of this tree doesn't change anything.
h._sift_down(0)
self.assertEqual(5, h._data[0])
self.assertEqual(1, h._data[1])
# Sifting down the last element of this tree doesn't change anything, either.
h._sift_down(1)
self.assertEqual(5, h._data[0])
self.assertEqual(1, h._data[1])
def test_sift_down_three_stable(self):
"""
Sifting down an element in a three-element heap, when the element is larger
than its children, is easy.
Hint: Be naive for now.
"""
h = MaxHeap()
h._data.append(10)
h._data.append(5)
h._data.append(1)
# Sifting down the root of this tree doesn't change anything.
h._sift_down(0)
self.assertEqual(10, h._data[0])
self.assertEqual(5, h._data[1])
self.assertEqual(1, h._data[2])
# Sifting down the second element of this tree doesn't change anything.
h._sift_down(1)
self.assertEqual(10, h._data[0])
self.assertEqual(5, h._data[1])
self.assertEqual(1, h._data[2])
# Sifting down the third element of this tree doesn't change anything.
h._sift_down(2)
self.assertEqual(10, h._data[0])
self.assertEqual(5, h._data[1])
self.assertEqual(1, h._data[2])
