算法中遇到的正则表达式

以你之姓@ 2024-03-23 09:56 8阅读 0赞

## 2. Java + Regular ##

#### 2.1. **空白字符(White Space)替换为`""`** ####

// 空白字符(White Space)替换为""
    String str = " \n\r\f\t  a  \n\r\f\t b \n\r\f\t  c \n\r\f\t ";
    str.replaceAll("\\s+", ""); //abc
    
    // 大写字符替换为空
    String str = "AaBbCcDdEeFfGgHhJj";
    str.replaceAll("[A-Z]", "") // abcdefghj
    
    // 小写字母替换为空
    String str = "AaBbCcDdEeFfGgHhJj";
    str.replaceAll("[a-z]", "") // ABCDEFGHJ

public String replaceAll(String regex, String replacement)
    public String replace(char oldChar, char newChar)
    public String replace(CharSequence target, CharSequence replacement)

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#### 2.2. [正则表达式如何匹配""][Link 1] ####

#### 2.3 [Java Matcher对象中 find() 与 matches() 的区别][Java Matcher_ find_ _ matches_] ####

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#### 2.4 断言是否`find()` ####

Predicate<String> predicate = Pattern.compile("dalian").asPredicate();
    
    System.out.println(predicate.test("welcome dalian")); //true
    System.out.println(predicate.test("welcome dalian1")); //true
    System.out.println(predicate.test("welcome dalia")); //false

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#### 2.5 按正则分割字符串 ####

Pattern pattern = Pattern.compile("dalian");
    Stream<String> stream = pattern.splitAsStream("Welcomedalianfordalian!");
    
    List<String> collect = stream.collect(Collectors.toList()); // [Welcome, for, !]

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## 算法题 ##

####  **\[中等\]  [HJ17.坐标移动][HJ17.]** ####

> 1、合法坐标为A(或者D或者W或者S) + 数字（两位以内）  
> 2、坐标之间以;分隔。  
> 3、非法坐标点需要进行丢弃。如AA10; A1A;  % ; YAD; 等。

List<String> strs = Arrays.stream(str.split(";")).collect(Collectors.toList());
    
    List<String> actions = strs.stream()
            .filter(a -> a != null && a.length() > 0)
            .filter(word -> word.matches("[WASD][0-9]{1,2}"))
            .collect(Collectors.toList());

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####  **\[中等\]  [HJ20.密码验证合格程序][HJ20.]** ####

包括大小写字母.数字.其它符号,以上四种至少三种

/**
     * 包括大小写字母.数字.其它符号,以上四种至少三种
     */
    private static boolean getMatch(String str) {
        
        int count = 0;
        Pattern p1 = Pattern.compile("[A-Z]");
        if (p1.matcher(str).find()) {
        
            count++;
        }
        Pattern p2 = Pattern.compile("[a-z]");
        if (p2.matcher(str).find()) {
        
            count++;
        }
        Pattern p3 = Pattern.compile("[0-9]");
        if (p3.matcher(str).find()) {
        
            count++;
        }
        Pattern p4 = Pattern.compile("[^a-zA-Z0-9]");
        if (p4.matcher(str).find()) {
        
            count++;
        }
        if (count >= 3) {
        
            return false;
        } else {
        
            return true;
        }
    }

--------------------

[Link 1]: https://blog.csdn.net/weixin_37646636/article/details/133281169
[Java Matcher_ find_ _ matches_]: https://blog.csdn.net/weixin_37646636/article/details/133281247
[HJ17.]: https://blog.csdn.net/weixin_37646636/article/details/128996493
[HJ20.]: https://blog.csdn.net/weixin_37646636/article/details/129000245