diff --git a/heaps/heap_sort.py b/heaps/heap_sort.py index 3b834a5..0766d96 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(log n) + Space Complexity: O(n) """ - pass \ No newline at end of file + heap = MinHeap() + for element in list: + heap.add(element) + + sorted_list = [] + while heap.store: + element = heap.remove() + sorted_list.append(element) + + return sorted_list \ No newline at end of file diff --git a/heaps/min_heap.py b/heaps/min_heap.py index f6fe4e0..c373738 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 @@ -19,19 +19,30 @@ def __init__(self): 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 + + node = HeapNode(key, value) + self.store.append(node) + 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(1) """ - pass + if len(self.store) == 0: + return None + + self.swap(0, len(self.store) - 1) + min = self.store.pop() + self.heap_down(0) + return min.value def __str__(self): @@ -44,10 +55,10 @@ 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): @@ -57,10 +68,25 @@ 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 + if index == 0: + return + + if index % 2 == 0: + # right node parent + parent_index = int((index - 2) / 2) + else: + # left node parent + parent_index = int((index - 1) / 2) + + if(parent_index < 0): + return + + if self.store[parent_index].key > self.store[index].key: + self.swap(parent_index, index) + self.heap_up(parent_index) def heap_down(self, index): """ This helper method takes an index and @@ -68,7 +94,17 @@ def heap_down(self, index): larger than either of its children and continues until the heap property is reestablished. """ - pass + left_child = index * 2 + 1 + right_child = index * 2 + 2 + + if len(self.store) > (left_child) and self.store[index].key > self.store[left_child].key: + self.swap(index, (left_child)) + self.heap_down((left_child)) + self.heap_down(index) + elif len(self.store) > (right_child) and self.store[index].key > self.store[right_child].key: + self.swap(index, (right_child)) + self.heap_down((right_child)) + self.heap_down(index) def swap(self, index_1, index_2):