6. Invert all words in the string.

6. Invert all words in the string.

Description:

1. There are only 26 uppercase or lowercase English letters in the characters that make up a word;

2. Characters that do not form a word are regarded as word spacers;

3. The inverted word spacer is required to be represented by a single space; if there are multiple spacers between adjacent words in the original string, only one space spacer is allowed after the inverted conversion;

4. The maximum length of each word is 20 letters;

Example

enter

I am a student

Output

student a am I

analysis

1. The god of regular expression manipulation of strings, the strongest on the surface, there is no one

2. Use regular expressions to filter out non-letter characters during keyboard entry
3. [^a-zA-Z] is to match non-a-z or non-A-Z characters in the target string
4. ^ [a-zA-Z is to match the characters starting with a-z or A-Z in brackets in the target string

Code

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String str;
		while ((str = br.readLine()) != null) {
			String[] arr = str.split("[^a-zA-Z]+");//利用正则表达式，去掉非字母
			StringBuilder ss = new StringBuilder();
			for (int i = arr.length - 1; i >= 0; i--) {
				if (i != 0)
					ss.append(arr[i]).append(" ");
			}
			System.out.println(ss.toString().trim());
		}
	}
}