How can I optimize this Python code for Codewars?

Question

The task in CodeWars is:

You are given a node that is the beginning of a linked list. This list
contains a dangling piece and a loop. Your objective is to determine
the length of the loop.

The Codewars compiler throws the error "Execution Timed Out (12000 ms)", although the code works as intended. As I got it, some function or method that I use are too slow, or I should choose different algorithm in my code?

My code:

def loop_size(node):
    #An array where I save all the elements not previously encountered
    arr = []
    currentElement = node
    i = 0
    #I check if I haven't met same element before
    while currentElement not in arr:
        arr.append(currentElement)
        currentElement = currentElement.next
        i += 1
    #Here I count the size of loop
    loopLength = i - arr.index(currentElement)
    return loopLength

Asked By: Lendwye

||

Source

Answer 1

This algorithm is better then prevous, because in the end, when we looking for element’s index, it’s faster to get it by using dictionary, because dictionary is a hash map, that search any item for time O(1). So all the problem in my previous solution, was the using arr.index(currentElement) , and this method is really time-consuming.

 def loop_size(node):
        myDict = dict()
        currentElement = node
        i = 0
        while currentElement not in myDict:
            myDict[currentElement] = i
            currentElement = currentElement.next
            i += 1
        loopSize = i - myDict.get(currentElement)
        return loopSize

Answered By: Lendwye

How can I optimize this Python code for Codewars?

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