java - 如何在 Java 中对单词进行所有可能的转换

Question

我目前正在开发一个程序，该程序将尝试根据单词中的字符对单词进行所有可能的转换。例如，如果单词是 hello，那么程序将打印出所有不同的变体，例如 hello、Hello、helloO、HelloO、h3ll0、H3lL0 等等，直到完成每个组合。这是我到目前为止制作的程序:

import java.io.*;

public class Transformer{
    String input = null;

    public Transformer(){
        run();
    }

    public void run(){
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        System.out.println("Please enter a word:");

        try {
            input = br.readLine();
        } catch (IOException e) {
            System.out.println("Error");
            System.exit(1);
        }

        //Convert String into char array
        char charArray[] = input.toCharArray();

        //Capitalise first letter
        if(Character.isLetter(charArray[0])){
            charArray[0] = Character.toUpperCase(charArray[0]);
        }
        System.out.println(charArray);

        //Reset transformation
        charArray = input.toCharArray();

        //Capitalise last letter
        if(Character.isLetter(charArray[charArray.length - 1])){
            charArray[charArray.length - 1] = Character.toUpperCase(charArray[charArray.length - 1]);
        }
        System.out.println(charArray);

        //Reset transformation
        charArray = input.toCharArray();


        //Iterate through charArray to make transformations to characters
        for(int i = 0; i < charArray.length; i++){
            if(charArray[i] == 'a'){
                charArray[i] = '@';
                System.out.println(charArray);
            }

            if(charArray[i] == 'o'){
                charArray[i] = '0';
                System.out.println(charArray);
            }

            if(charArray[i] == 'e'){
                charArray[i] = '3';
                System.out.println(charArray);
            }

            if(charArray[i] == 's'){
                charArray[i] = '5';
                System.out.println(charArray);
            }

            if(charArray[i] == 'i'){
                charArray[i] = '1';
                System.out.println(charArray);
            }

            if(charArray[i] == 'l'){
                charArray[i] = '7';
                System.out.println(charArray);
            }
        }
    }
}

问题是，这只会创建有限数量的转换并将它们相继添加，而不是一次进行一个转换，然后进行两个，依此类推。我能想到的唯一解决方案是永无止境的 if 语句列表，但即便如此，我也不确定如何跟踪更改。实现这一目标的最佳方法是什么？

Answer 1

我告诉过你这样的事情:

public class WordTransformer {

    private HashMap<Character, char[]> transformMap = new HashMap<Character, char[]>();
    {
        transformMap.put('h', new char[]{'H', 'h'});
        transformMap.put('e', new char[]{'3', 'E'});
        transformMap.put('l', new char[]{'I', 'L'});
        transformMap.put('o', new char[]{'0', 'O'});
    }

    public List<String> doTransform(String s){
        char[] stringChars = s.toCharArray();
        List<String> versions = new ArrayList<String>();
        doTransform(s, stringChars, 0, versions);
        return versions;
    }

    //This method is recursive
    private void doTransform(String s, char[] stringChars, int index,
        List<String> versions){

        //if we reached the end of string in current iteration
        //add generated variant into list
        if(index==s.length()){
            versions.add(new String(stringChars));
            return;
        }

        char c = s.charAt(index);
        if(transformMap.containsKey(c)){
            char[] transforms = transformMap.get(c);
            for(char t : transforms){
                stringChars[index] = t;
                //And this is recursive invocation, that means method calls itself
                doTransform(s, stringChars, index+1, versions);
            }
        }else {
            //if there is no such character in transform map, process next index
            doTransform(s, stringChars, index+1, versions);
        }
    }

}

请注意，私有(private)方法 doTransform 会自行调用。这称为递归方法。另请注意，我们将原始字符串和 chars 数组传递给此方法。 Array - 是一个地方，我们在这里构建原始字符串的每个版本。用法:

WordTransformer transformer = new WordTransformer();
List<String> list = transformer.doTransform("hello");
for(String s : list){
    System.out.println(s);
}

希望这会有所帮助。