如何找到最大在Python中一个字符序列连续重复多少次? [英] How to find the max. number of times a sequence of characters repeats consecutively in Python?

问题描述

我正在研究cs50/pset6/dna项目.我正在努力寻找一种方法来分析一系列字符串，并收集某个特定字符序列连续重复的最大次数.这是一个示例:

I'm working on a cs50/pset6/dna project. I'm struggling with finding a way to analize a sequence of strings, and gather the maximum number of times a certain sequence of characters repeats consecutively. Here is an example:

字符串: JOKHCNHBVDBVDBVDJHGSBVDBVD

我应该寻找的字符序列: BVD

Sequence of characters I should look for: BVD

结果:我的函数应该能够返回 3 ，因为在某个点上，字符 BVD 连续重复了三遍，即使我又重复了两次，应该寻找重复次数最多的时间.如果您仍然需要更好的解释，请查看此视频的第一个 1:16 :

Result: My function should be able to return 3, because in one point the characters BVD repeat three times consecutively, and even though it repeats again two times, I should look for the time that it repeats the most number of times. If you still need a better explanation, please look at the first 1:16 of this video: https://www.youtube.com/watch?time_continue=221&v=j84b_EgntcQ&feature=emb_title

如果您能帮助我，我会很乐意，谢谢！

I would LOVE if you could help, thanks!

推荐答案

这有点la脚，但是一种蛮力"的方式是仅检查是否存在最长的子字符串.一旦找到子字符串，请跳出循环:

It's a bit lame, but one "brute-force"ish way would be to just check for the presence of the longest substring possible. As soon as a substring is found, break out of the loop:

编辑-使用函数可能更直接:

EDIT - Using a function might be more straight forward:

def get_longest_repeating_pattern(string, pattern):
    if not pattern:
        return ""
    for i in range(len(string)//len(pattern), 0, -1):
        current_pattern = pattern * i
        if current_pattern in string:
            return current_pattern
    return ""

string = "JOKHCNHBVDBVDBVDJHGSBVDBVD"
pattern = "BVD"


longest_repeating_pattern = get_longest_repeating_pattern(string, pattern)
print(len(longest_repeating_pattern))

编辑-说明:

首先，只是一个简单的for循环，该循环从较大的数字开始，然后下降到较小的数字.例如，我们从5开始，然后下降到0(但不包括0)，步长为-1:

First, just a simple for-loop that starts at a larger number and goes down to a smaller number. For example, we start at 5 and go down to 0 (but not including 0), with a step size of -1:

>>> for i in range(5, 0, -1):
    print(i)

    
5
4
3
2
1
>>> 

如果 string ="JOKHCNHBVDBVDBVDJHGSBVDBVD" ，则 len(string)为 26 ，如果 pattern ="BVD"; ，则 len(pattern)是 3 .

if string = "JOKHCNHBVDBVDBVDJHGSBVDBVD", then len(string) would be 26, if pattern = "BVD", then len(pattern) is 3.

返回我的原始代码:

for i in range(len(string)//len(pattern), 0, -1):

输入数字:

for i in range(26//3, 0, -1):

26//3 是一个整数除法，其结果为 8 ，因此变为:

26//3 is an integer division which yields 8, so this becomes:

for i in range(8, 0, -1):

因此，这是一个从 8 到 1 的for循环(请记住，它不会下降到 0 ). i 采用每次迭代的新值，首先是 8 ，然后是 7 ，等等.

So, it's a for-loop that goes from 8 to 1 (remember, it doesn't go down to 0). i takes on the new value for each iteration, first 8 , then 7, etc.

在Python中，您可以乘以"字符串，就像这样:

In Python, you can "multiply" strings, like so:

>>> pattern = "BVD"
>>> pattern * 1
'BVD'
>>> pattern * 2
'BVDBVD'
>>> pattern * 3
'BVDBVDBVD'
>>> 

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