游程编码Python [英] Run Length Encoding Python

问题描述

我遇到的问题是:

编写一个函数，该函数将一个字符列表作为参数，并返回一个反映该列表的游程长度编码的列表.返回列表中的元素遵循以下模式:偶数索引包含字符，奇数索引包含连续重复字符的次数.将您的函数命名为runLengthEncoding(myList).

Write a function that takes, as an argument, a list of characters and returns a list reflecting the run-length encoding of that list. The elements in the returned list follow the following pattern: the even indices contain the characters and the odd indices contain the number of times the character is repeated consecutively. Name your function runLengthEncoding(myList).

例如， runLengthEncoding([aaabbccd])应该返回 [a，3，b，2，c，2，d，1] .

这里是我所拥有的，但我不知道出了什么问题:

Here is what I have, but I can't figure out what is wrong:

def runLengthEncoding(myList):
    aList = []
    count = 1
    for i in range(0, len(myList)):
        if myList[i] == myList[i - 1]:
            count = count + 1
        else:
            aList.append((count, myList[i - 1]))
            count = 1
        if i == len(myList) - 1:
            aList.append((count, myList[i]))
    return aList

推荐答案

您几乎拥有它，但是需要进行一些更改.调用 runLengthEncoding([aaabbccd])将不起作用，因为它将 aabbccd 作为变量而不是字符串进行调用.如果用引号将方括号替换，则将以字符串形式提供预期的输入(在python中也称为字符列表).

You almost had it, there are a couple of changes necessary however. Calling runLengthEncoding([aaabbccd]) will not work as it is calling aabbccd as a variable, not as a string. If you replace the square brackets with quotation marks, you will have the intended input as a string (also known in python as a list of chars).

此外，根据您对函数输出格式的要求，您当前正在输出一个元组列表，而不是一个带有其计数的char的向上列表.要按照问题中的指定输出，您可以将 aList.append((count，myList [i-1]))行更改为:

Also, depending on how picky you have to be on the format of the output of the function, you are currently outputting a list of tuples, instead of a straight up list of the chars with their counts. To output this as specified in the question, you can change your aList.append((count, myList[i-1])) lines to be:

aList.append(myList[i-1])
aList.append(count)   

最后，您发布的代码唯一的错误是您希望for循环从1而不是0开始.这意味着 i-1 将从0开始-1.这是工作的修改后的代码:

And finally, the only thing wrong with the code you posted was that you want your for loop to start at 1 rather than 0. This will mean that the i-1 will start at 0 instead of -1. Here is the working modified code:

def runLengthEncoding(myList):
    aList = []
    count = 1
    for i in range(1, len(myList)):
        if myList[i] == myList[i - 1]:
            count = count + 1
        else:
            aList.append((count, myList[i - 1]))
            count = 1
            if i == len(myList) - 1:
                aList.append((count, myList[i]))
    return aList

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