Binary Heap

Author: ivanmmarkovic

trees/binary-heap.py

@@ -0,0 +1,65 @@
+
+class BinaryHeap:
+    def __init__(self):
+        self.pointer: int = 0
+        self.heap: list = [None]
+
+    def is_empty(self) -> bool:
+        return self.pointer == 0
+
+    def insert(self, item):
+        self.heap.append(item)
+        self.pointer += 1
+        self.perc_up(self.pointer)
+
+    def perc_up(self, index: int):
+        while index // 2 > 0:
+            if self.heap[index] < self.heap[index // 2]:
+                self.heap[index], self.heap[index // 2] = self.heap[index // 2], self.heap[index]
+            index = index // 2
+
+    def get_min(self):
+        if self.is_empty():
+            raise Exception("Heap is empty")
+        return self.heap[1]
+
+    def delete_min(self):
+        if self.is_empty():
+            raise Exception("Heap is empty")
+        ret_value: int = self.heap[1]
+        self.heap[1] = self.heap[self.pointer]
+        self.heap.pop()
+        self.pointer -= 1
+        self.perc_down(1)
+        return ret_value
+
+    def perc_down(self, index: int):
+        while index * 2 <= self.pointer:
+            swap_index: int = self.find_swap_index(index)
+            if self.heap[swap_index] < self.heap[index]:
+                self.heap[swap_index], self.heap[index] = self.heap[index], self.heap[swap_index]
+            index = swap_index
+
+    def find_swap_index(self, index: int) -> int:
+        if index * 2 + 1 > self.pointer:
+            return index * 2
+        else:
+            if self.heap[index * 2] <= self.heap[index * 2 + 1]:
+                return index * 2
+            else:
+                return index * 2 + 1
+
+    def build_heap(self, nums: list):
+        for n in nums:
+            self.insert(n)
+
+
+h: BinaryHeap = BinaryHeap()
+h.insert(10)
+h.insert(1)
+h.insert(3)
+print(h.heap)  # [None, 1, 10, 3]
+print(h.get_min())  # 1
+
+while not h.is_empty():
+    print(h.delete_min())