hello-algo/en/codes/python/chapter_heap/heap.py

"""
File: heap.py
Created Time: 2023-02-23
Author: krahets (krahets@163.com)
"""

import sys
from pathlib import Path

sys.path.append(str(Path(__file__).parent.parent))
from modules import print_heap

import heapq


def test_push(heap: list, val: int, flag: int = 1):
    heapq.heappush(heap, flag * val)  # Element enters heap
    print(f"\nAfter element {val} enters heap")
    print_heap([flag * val for val in heap])


def test_pop(heap: list, flag: int = 1):
    val = flag * heapq.heappop(heap)  # Top element exits heap
    print(f"\nAfter top element {val} exits heap")
    print_heap([flag * val for val in heap])


"""Driver Code"""
if __name__ == "__main__":
    # Initialize min heap
    min_heap, flag = [], 1
    # Initialize max heap
    max_heap, flag = [], -1

    print("\nThe following test cases are for max heap")
    # Python's heapq module implements min heap by default
    # Consider negating the elements before entering the heap, which can reverse the size relationship, thus implementing max heap
    # In this example, flag = 1 corresponds to min heap, flag = -1 corresponds to max heap

    # Elements enter heap
    test_push(max_heap, 1, flag)
    test_push(max_heap, 3, flag)
    test_push(max_heap, 2, flag)
    test_push(max_heap, 5, flag)
    test_push(max_heap, 4, flag)

    # Get top element
    peek: int = flag * max_heap[0]
    print(f"\nTop element is {peek}")

    # Top element exits heap
    test_pop(max_heap, flag)
    test_pop(max_heap, flag)
    test_pop(max_heap, flag)
    test_pop(max_heap, flag)
    test_pop(max_heap, flag)

    # Get heap size
    size: int = len(max_heap)
    print(f"\nNumber of heap elements is {size}")

    # Check if heap is empty
    is_empty: bool = not max_heap
    print(f"\nIs heap empty {is_empty}")

    # Input list and build heap
    # Time complexity is O(n), not O(nlogn)
    min_heap = [1, 3, 2, 5, 4]
    heapq.heapify(min_heap)
    print("\nAfter inputting list and building min heap")
    print_heap(min_heap)