Python | Leetcode Python题解之第315题计算右侧小于当前元素的个数

题目：

题解：

import numpy as np
from bisect import bisect_left

class Solution:
    max_len =  10000
    c = []
    buckets = []

    def countSmaller(self, nums: List[int]) -> List[int]:
        self.c = [0 for _ in range(len(nums) + 5)]
        counts = [0 for _ in range(len(nums))]
        nums = self.discretization(nums)
        for i in range(len(nums) - 1, -1, -1):
            num = nums[i]
            counts[i] = self.query(num-1)
            self.updateC(num)
        return counts

    def updateC(self, pos):
        while pos < len(self.c):
            self.c[pos] += 1
            pos += self.lowbit(pos)

    def lowbit(self, x):
        """获取更新范围"""
        return x & (-x)

    def query(self, pos):
        """查询前缀和"""
        val = 0
        while pos > 0:
            val += self.c[pos]
            pos -= self.lowbit(pos)
        return val

    def getMappingList(self, nums):
        """列表去重排序"""
        return list(sorted(set(nums)))

    def discretization(self, nums):
        """将nums进行离散化变换"""
        mapping = self.getMappingList(nums)
        return [bisect_left(mapping, num) + 1 for num in nums]