557. 反转字符串中的单词 III

给定一个字符串，你需要反转字符串中每个单词的字符顺序，同时仍保留空格和单词的初始顺序。

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/reverse-words-in-a-string-iii
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

import java.util.Scanner;

class Solution {

    private static void swap(char[] str, int a, int b) {
        char tmp = str[a];
        str[a] = str[b];
        str[b] = tmp;
    }

    private static void reverse(char[] str, int left, int right) {
        while (left < right) {
            swap(str, left++, right--);
        }
    }

    public static String reverseWords(String s) {
        char[] str = s.toCharArray();
        int start = 0;

        for (int i = 0; i < str.length; ++i) {
            if (str[i] == ' ') {
                reverse(str, start, i - 1);
                start = i + 1;
            }
        }
        reverse(str, start, str.length - 1);
        return new String(str);
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            System.out.println(reverseWords(in.nextLine()));
        }
    }
}