diff --git a/heaps/heap_sort.py b/heaps/heap_sort.py index 3b834a5..482065b 100644 --- a/heaps/heap_sort.py +++ b/heaps/heap_sort.py @@ -1,8 +1,17 @@ - +from heaps.min_heap import MinHeap def heap_sort(list): """ This method uses a heap to sort an array. - Time Complexity: ? - Space Complexity: ? + Time Complexity: O(n log n) + Space Complexity: O(n) """ - pass \ No newline at end of file + heap = MinHeap() + for elem in list: + heap.add(elem) + + hold = [] + while heap.store: + elem = heap.remove() + hold.append(elem) + + return hold \ No newline at end of file diff --git a/heaps/min_heap.py b/heaps/min_heap.py index 0095872..16c3391 100644 --- a/heaps/min_heap.py +++ b/heaps/min_heap.py @@ -1,5 +1,5 @@ class HeapNode: - + def __init__(self, key, value): self.key = key self.value = value @@ -7,7 +7,7 @@ def __init__(self, key, value): def __str__(self): return str(self.value) - def __repr__(self): + def __repr__(self): # ? return str(self.value) @@ -17,25 +17,32 @@ class MinHeap: def __init__(self): self.store = [] - def add(self, key, value = None): """ This method adds a HeapNode instance to the heap If value == None the new node's value should be set to key - Time Complexity: ? - Space Complexity: ? + Time Complexity: O(log n) + Space Complexity: O(1) """ - pass + if value == None: + value = key + + self.store.append(HeapNode(key, value)) + self.heap_up(len(self.store) -1) def remove(self): """ This method removes and returns an element from the heap maintaining the heap structure - Time Complexity: ? - Space Complexity: ? + Time Complexity: O(log n) + Space Complexity: O(log n) """ - pass + if self.empty(): + return None + self.swap(0, len(self.store) - 1) + min = self.store.pop(len(self.store) - 1) + self.heap_down(0) + return min.value - def __str__(self): """ This method lets you print the heap, when you're testing your app. """ @@ -46,10 +53,10 @@ def __str__(self): def empty(self): """ This method returns true if the heap is empty - Time complexity: ? - Space complexity: ? + Time complexity: O(1) + Space complexity: O(1) """ - pass + return len(self.store) == 0 def heap_up(self, index): @@ -59,10 +66,19 @@ def heap_up(self, index): property is reestablished. This could be **very** helpful for the add method. - Time complexity: ? - Space complexity: ? + Time complexity: O(log n) + Space complexity: O(log n) """ - pass + parent_index = (index - 1) // 2 + + if index == 0: + return None + + node = self.store[index] + + if self.store[parent_index].key > node.key: + self.swap(parent_index, index) + self.heap_up(parent_index) def heap_down(self, index): """ This helper method takes an index and @@ -70,7 +86,21 @@ def heap_down(self, index): larger than either of its children and continues until the heap property is reestablished. """ - pass + left_child = (2 * index) + 1 + right_child = (2 * index) + 2 + + if left_child < len(self.store): + if right_child < len(self.store): + if self.store[left_child].key < self.store[right_child].key: + min_child = left_child + else: + min_child = right_child + else: + min_child = left_child + + if self.store[index].key > self.store[min_child].key: + self.swap(index, min_child) + self.heap_down(min_child) def swap(self, index_1, index_2):