python索引如何影响o-notation的运行时？

Question

I am new to O-notation and am trying to find the worst-case runtime for some of my codes. The only issue is that I'm confused on how O-notation runs with indexing and appending so I thought I'd ask for help with the following sample codes:

def sums_1(L):
  n = len(L)
  tot = 0
  M = []
  for i in L[:n//2]:
    M.append(i)
  for i in L[n//2:]:
    M.extend(L)
  return sum(M)

def sums_2(s):
  def help_e(s, pos):
    if pos >= len(s):
      return ''
    return help_e(s, pos+1) + s[pos]
  return help_e(s, 0)

I think both codes would run o(n) times but I wanted some clarification on indexing and how that may affect the runtime, thanks!

Answer 1

在这里你有几乎所有 python 数据结构操作的 big-o 符号的 wiki 文件： https : //wiki.python.org/moin/TimeComplexity