常见数据结构与算法的 Python 实现

1. 排序

• 快速排序（quick sort）

  • 形式一：借助 partition 辅助函数

  def partition(seq):
      pivot, seq = seq[0], seq[1:]
      low = [x for x in seq if x <= pivot]
      high = [x for x in seq if x not in low]
      return low, pivot, high
  
  def qsort(seq):
      if len(seq) <= 1: return seq
      low, pivot, high = partition(seq)
      return qsort(low)+[pivot]+qsort(high)

  • 形式二：直接返回数组

  def qsort(arr):
      if len(arr) <= 1:
          return arr
      pivot = arr[len(arr)//2]
      left = [x for x in arr if x < pivot]
      middle = [x for x in arr if x == pivot]
      right = [x for x in arr if x > pivot]
      return qsort(left) + middle + qsort(right)