创建列表的多个副本的最快方法 [英] Fastest way to create multiple copies of a list

问题描述

我正在为我的迷宫求解器开发一种广度优先的搜索算法，到目前为止，它一直在工作.我通过复制前一个堆栈并将当前值附加到当前堆栈来跟踪当前堆栈.

I am working on a breadth-first search algorithm for my maze solver and it is working so far. I am keeping track of the current stack by copying the previous one and appending the current value to it.

由于复制列表需要花费大量时间，因此我想在一次操作中创建列表的多个副本.

Since copying list takes a great amount of time I would like to create multiple copies of the list within one operation.

• 复制列表并将其分配给多个变量.

• Copy the list and assign it to multiple variables.

l = [1, 2, 3]
a = b = c = l[:]  # Just creates references and no individual lists

使用具有copy函数(比list[:]更快)的numpy数组.

Use numpy arrays with copy function (faster than list[:]).

创建一个列表的多个副本的最快方法是什么?

What is the fastest way to create multiple copies of one list?

推荐答案

请勿在堆栈中使用普通的Python列表.使用Lisp样式的链表，因此您的堆栈彼此共享其大部分结构，并且使用额外的元素构建新堆栈的时间是恒定的:

Don't use ordinary Python lists for your stacks. Use Lisp-style linked lists, so your stacks share most of their structure with each other and building a new stack with an additional element is constant time:

def empty_stack():
    return ()
def push(stack, item):
    return (item, stack)
def stack_to_list(stack):
    l = []
    while stack:
        item, stack = stack
        l.append(item)
    return l[::-1]

在这里，push以恒定的时间运行并生成新的堆栈，而不会改变旧堆栈，因此您可以在旧堆栈上重复调用push而不复制它.

Here, push runs in constant time and produces a new stack, without mutating the old, so you can call push on the old stack repeatedly without copying it.

这篇关于创建列表的多个副本的最快方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！