python 实现bitmap，排序

Posted 2021-01-07 butter-007

#python整数类型默认是有符号类型。可用位数是31位。

import math


class Bitmap(object):
    def __init__(self, max):
        self.size = math.ceil(max / 31)
        self.array = [0 for i in range(self.size)]

    def calcElemIndex(self, num):
        return num // 31

    def calcBitIndex(self, num):
        return num % 31

    def set(self, num):
        elemIndex = self.calcElemIndex(num)
        byteIndex = self.calcBitIndex(num)
        elem = self.array[elemIndex]
        self.array[elemIndex] = elem | (1 << byteIndex)#左移相当于乘以2的次方 

    def clean(self, num):
        elemIndex = self.bitmap.calcElemIndex(num)
        byteIndex = self.bitmap.calcBitIndex(num)
        elem = self.array[elemIndex]
        self.array[elemIndex] = elem & (~(1 << byteIndex))#清除改位，不影响其余位

    def test(self, num):
        elemIndex = self.calcElemIndex(num)
        byteIndex = self.calcBitIndex(num)
        elem = self.array[elemIndex]
        if elem & (1 << byteIndex):
            return True
        return False


if __name__ == ‘__main__‘:
    # bitmap = Bitmap(90)
    # print("需要%d个元素。" % bitmap.size)
    # print("存储在第%d个元素上的第%d位上面" % (bitmap.calcElemIndex(47), bitmap.calcBitIndex(47)))
    max = 688
    suffle_array = [0, 67, 1, 45, 187, 65, 58, 101, 33, 252, 688, 145, 254, 487]
    result = []
    bitmap = Bitmap(688)
    for i in suffle_array:
        bitmap.set(i)
    for i in range(max + 1):
        if bitmap.test(i):
            result.append(i)
    print(result)