【python刷题】数据流中的中位数

思路：维护一个大顶堆和一个小顶堆；

import heapq
class MedianFinder(object):
    def __init__(self):
        """
        initialize your data structure here.
        """
        self.len = 0
        self.minheap = []
        self.maxheap = []

    def addNum(self, num):
        """
        :type num: int
        :rtype: None
        """
        self.len += 1
        heapq.heappush(self.maxheap, -heapq.heappushpop(self.minheap, num))
        if len(self.maxheap) > len(self.minheap):
            heapq.heappush(self.minheap, -heapq.heappop(self.maxheap))

    def findMedian(self):
        """
        :rtype: float
        """
        if self.len & 1 == 0:
            return (self.minheap[0] - self.maxheap[0]) / 2.0
        return self.minheap[0]

m = MedianFinder()
m.addNum(2)
print(m.maxheap, m.minheap)
m.addNum(3)
print(m.maxheap, m.minheap)
print(m.findMedian())
m.addNum(4)
print(m.maxheap, m.minheap)
print(m.findMedian())

结果：

[] [2]
[-2] [3]
2.5
[-2] [3, 4]
3