Python でのヒープと優先キューの使用シナリオは何ですか?

import heapq

def top_k_smallest(nums, k):
    heap = []
    for num in nums:
        heapq.heappush(heap, num)
        if len(heap) > k:
            heapq.heappop(heap)
    return heap

nums = [5, 3, 8, 2, 7, 1, 9]
k = 3
result = top_k_smallest(nums, k)
print(result)  # 输出 [3, 2, 1]

import heapq

def merge_sorted_arrays(arrays):
    result = []
    pq = []
    for array in arrays:
        if array:
            heapq.heappush(pq, (array[0], array))
    
    while pq:
        smallest, array = heapq.heappop(pq)
        result.append(smallest)
        if array[1:]:
            heapq.heappush(pq, (array[1], array[1:]))
    
    return result

arrays = [[1, 3, 5], [2, 4, 6], [0, 7, 8]]
result = merge_sorted_arrays(arrays)
print(result)  # 输出 [0, 1, 2, 3, 4, 5, 6, 7, 8]

import heapq

def median(nums):
    min_heap = []
    max_heap = []
    for num in nums:
        if len(max_heap) == 0 or num <= -max_heap[0]:
            heapq.heappush(max_heap, -num)
        else:
            heapq.heappush(min_heap, num)
        
        if len(max_heap) > len(min_heap) + 1:
            heapq.heappush(min_heap, -heapq.heappop(max_heap))
        elif len(min_heap) > len(max_heap):
            heapq.heappush(max_heap, -heapq.heappop(min_heap))
    
    if len(max_heap) > len(min_heap):
        return -max_heap[0]
    elif len(min_heap) > len(max_heap):
        return min_heap[0]
    else:
        return (-max_heap[0] + min_heap[0]) / 2

nums = [4, 2, 5, 7, 1, 8, 3, 6]
result = median(nums)
print(result)  # 输出 4.5