嵌套表达式导致堆栈溢出

def factorial(n, acc=1):
    if n == 0:
        return acc
    return factorial(n - 1, n * acc)

def factorial(n):
    result = 1
    for i in range(1, n + 1):
        result *= i
    return result

import sys
sys.setrecursionlimit(10000)

def merge_sort(arr):
    if len(arr) <= 1:
        return arr
    
    mid = len(arr) // 2
    left = merge_sort(arr[:mid])
    right = merge_sort(arr[mid:])
    
    return merge(left, right)

def merge(left, right):
    result = []
    i = j = 0
    
    while i < len(left) and j < len(right):
        if left[i] < right[j]:
            result.append(left[i])
            i += 1
        else:
            result.append(right[j])
            j += 1
    
    result.extend(left[i:])
    result.extend(right[j:])
    return result