题解 | 字符串变形

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param s string字符串 
     * @param n int整型 
     * @return string字符串
     */
    public String trans (String s, int n) {
        // write code here
        List<String> list = split(s, n);

        final StringBuilder builder = new StringBuilder();

        for(int i=list.size()-1; i>=0; i--){
            String current = list.get(i);
            System.out.println(current);
            builder.append(transWord(current));
        }
    
        return builder.toString();
    }

    public List<String> split(String s, int n){
        n = n >= s.length() ? s.length() : n;
        List<String> list = new ArrayList<>(n);
        char[] carr = s.toCharArray();
        String currentWord = "";
        for(int i=0; i < n; i++){
            if(s.charAt(i) == ' '){
                if(!currentWord.isEmpty()){
                    list.add(currentWord);
                    currentWord = "";
                }
                list.add(" ");
            }else{
                currentWord += s.charAt(i);
            }
        }
        if(!currentWord.isEmpty()){
            list.add(currentWord);
        }
        return list;
    }

    public String transWord(String word) {
        char[] carr = word.toCharArray();
        char[] ncarr = new char[word.length()];
        int index = 0;
        int distance = 'a' - 'A';
        for( int i = 0; i < carr.length; i++){
            char ch = word.charAt(i);
            if( ch >= 'a' && ch <= 'z' ){
                ch -= distance;
            }else if( ch >= 'A' && ch <= 'Z'){
                ch += distance;
            }
            ncarr[index++] = ch;
        }
        return new String(ncarr);
    }
}