Python in the heap heapq

Indeed, Python no separate stack type, and only a few functions of the module stack operation contains. This module is called heapq (where q represents the queue), a small top default heap. Python is not the big top of the heap implementation.

Commonly used functions

function	description
heappush(heap, x)	The pile press-x
heappop(heap)	From the pop-up stack smallest elements (top element)
heapify([1,2,3])	Make a list of characteristics with heap
heapreplace(heap, x)	Pop smallest elements (top element), and the stack pressed x
nlargest(n, iter)	Iter returns the largest element in the n
nsmallest(n, iter)	Iter returns the smallest element of n

heappop pop smallest element (always at index 0, \ stack), and to ensure that the smallest remaining element at index 0 (the stack holding feature).

heapreplace equal to heappop then heappush, but calls were faster than them.

Stack operation time complexity, the following is a heap of implementation: binary heap, Fibonacci heap, Fibonacci heap ...... strict, common module is used in Fibonacci heap "

Code Example:

from heapq import *

class KthLargest:

    def __init__(self, k: int, nums: List[int]):
        self.k = k
        self.q = []
        for x in nums:
            self.add(x)

    def add(self, val: int) -> int:
        if len(self.q) < self.k:        # 堆没满，加入堆
            heappush(self.q, val)
        elif val > self.q[0]:           # val大于堆顶元素（第K大），踢掉堆顶元素，加入val
            heapreplace(self.q, val)
        return self.q[0]                # 堆顶

import heapq
a = [2,4,1,5,6,3]
heapq.heapify(a)
print(a)       # [1, 4, 2, 5, 6, 3]

import heapq
a = [2,4,1,5,6,3]
heapq.heapify(a)
b = heapq.heappop(a)
print(a)      # [2, 4, 3, 5, 6]
print(b)      # 1