java - 如何检查整数中的重复序列

Question

我有一个字母数字字符串，我想检查其中的模式重复是否只是整数。它们应该是连续的。

示例

1. 12341234qwe 应该告诉我 1234 重复了。
2. 1234qwe1234 应该 NOT 告诉我 1234 是重复的，因为它不连续。
3. 12121212 应该被视为 12 被重复，因为这是第一个被发现被重复的集合。但是如果有一种算法会发现 1212 作为 12 之前的重复集，那么我猜它必须在 1212 上再次执行这些步骤。

我认为我可以通过迭代和比较来存储整数部分 ( <= '0' && >= '9')在不同的StringBuilder .然后我读到了关于对字符串执行 FFT 的文章，它显示了重复的模式。但是我不知道如何在 Java 中执行 FFT 并寻找结果，而且，我希望在不去信号处理的情况下尝试这样做。我阅读了有关 KMP 模式匹配的信息，但这仅适用于给定的输入。有没有其他方法可以做到这一点？

Answer 1

我认为你可以借助正则表达式来解决这个问题。考虑这样的代码:

String arr[] = {"12341234abc", "1234foo1234", "12121212", "111111111", "1a1212b123123c12341234d1234512345"};
String regex = "(\\d+?)\\1";
Pattern p = Pattern.compile(regex);
for (String elem : arr) {
    boolean noMatchFound = true;
    Matcher matcher = p.matcher(elem);
    while (matcher.find()) {
        noMatchFound = false;
        System.out.println(elem + " got repeated: " + matcher.group(1));
    }
    if (noMatchFound) {
        System.out.println(elem + " has no repeation");
    }
}

输出:

abc12341234abc got repeated: 1234
1234foo1234 has no repeation
12121212 got repeated: 12
12121212 got repeated: 12
111111111 got repeated: 1
111111111 got repeated: 1
111111111 got repeated: 1
111111111 got repeated: 1
1a1212b123123c12341234d1234512345 got repeated: 12
1a1212b123123c12341234d1234512345 got repeated: 123
1a1212b123123c12341234d1234512345 got repeated: 1234
1a1212b123123c12341234d1234512345 got repeated: 12345

说明:

使用的正则表达式是 (\\d+?)\\1 where

\\d        - means a numerical digit
\\d+       - means 1 or more occurrences of a digit
\\d+?      - means reluctant (non-greedy) match of 1 OR more digits
( and )    - to group the above regex into group # 1
\\1        - means back reference to group # 1
(\\d+?)\\1 - repeat the group # 1 immediately after group # 1