频率分析算法 [英] frequency analysis algorithm

问题描述

我想编写一个Java程序，该程序搜索密文并返回密文中字符的频率计数，例如密文: "jshddllpkeldldwgbdpked"将具有以下结果:

I want to write a java program that searches through a cipher text and returns a frequency count of the characters in the cipher, for example the cipher: "jshddllpkeldldwgbdpked" will have a result like this:

出现2个字母:

pk = 2，ke = 2，ld = 2

pk = 2, ke = 2, ld = 2

3次出现字母:

pke = 2.

有什么算法可以让我尽可能高效地做到这一点?

Any algorithm that allows me to do this as efficiently as possible?

推荐答案

地图策略是一种很好的策略，但我会选择HashMap<String, Integer>，因为它是要计算的元组.

The map strategy is a good one, but I'd go for HashMap<String, Integer>, since it's tuples of characters being counted.

遍历密文中的字符，可以保存最后的X个字符，这将为您提供所有出现的长度为X + 1的子字符串的映射.

Iterating over the characters in the ciphertext, you can save the last X characters and that will give you a map over all occurrences of substrings of length X+1.

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