题解 | #单词倒排#

import java.util.*;
import java.lang.*;

/**
难点：
    while(i>=0 && Character.isLetter(c)){
                i--;
                c = str.charAt(i);
            }
            res.append(str.substring(i+1,j+1)+" ");
    这样写会出现越界错误，因为当i=0时，i--会变成-1，str.charAt(-1)会报错。所以不如直接去掉c
 */
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String str = in.nextLine();
        StringBuilder res = new StringBuilder();
        int n = str.length();
        int i = n - 1;
        int j = n - 1;

        while (i >= 0) {
            while (i >= 0 && Character.isLetter(str.charAt(i))) {
                i--;
            }
            res.append(str.substring(i + 1, j + 1) + " ");

            while (i >= 0 && !Character.isLetter(str.charAt(i))) {
                i--;
            }
            j = i;
        }
        System.out.println(res.toString().trim());
    }
}