题解 | #单词倒排#

import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {

        String s = "";
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            s = in.nextLine();
        }
        result(s);
    }


    private static void result(String s) {

        List<String> list = init(s);
        int size = list.size();
        for (int i = size - 1; i >= 0; i--) {
            if (i == 0) {
                System.out.print(list.get(i));
            } else {
                System.out.print(list.get(i) + " ");
            }
        }
    }

    private static List<String> init(String s) {

        List<String> list = new LinkedList<>();
        int len = s.length();
        char[] arr = s.toCharArray();
        for (int i = 0; i < len; i++) {
            char c = arr[i];
            if (!(c >= 'A' && c <= 'Z') && !(c >= 'a' && c <= 'z')) {
                arr[i] = ' ';
            }
        }

        addList(list, arr);
        return list;
    }

    private static void addList(List<String> list, char[] arr) {

        int len = arr.length;
        StringBuffer b = new StringBuffer();
        for (int i = 0; i < len; i++) {
            char c = arr[i];
            if (c != ' ') {
                b = b.append(c);
                if (i == len - 1 || (i + 1 < len && arr[i + 1] == ' ')) {
                    list.add(b.toString());
                    b = new StringBuffer();
                }
            }
        }

    }

}