题解 | #单词倒排#

package main

import (
	"fmt"
	"strings"
    "bufio"
    "os"
)

func isLetter(ch byte) bool {
    return ('A' <= ch && ch <= 'Z') || ('a' <= ch && ch <= 'z')
}

func reverseWords(s string) string {
    size := len(s)
    s = strings.Trim(s, " ")
    
    slow, fast := 0, 0
    var words []string
    for fast < size {
        if !isLetter(s[fast]) {
            words = append(words, s[slow:fast])
            for !isLetter(s[fast]) && fast<size {fast++}
            slow = fast
        } else {
            fast++
        }
    }

    if fast == size && isLetter(s[fast-1]) {
        words = append(words, s[slow:fast])
    }

    for i,j:=0,len(words)-1; i<j; i,j=i+1,j-1 {
        words[i], words[j] = words[j], words[i]
    }

    return strings.Join(words, " ")
}

func main() {
    var s string

    inputReader := bufio.NewReader(os.Stdin)
    line, _, _ := inputReader.ReadLine()

    s = string(line)

    fmt.Println(reverseWords(s))
}

// 本题输入为一行带空格的字符串，所以采用 inputReader.ReadLine()