Medium 186题 Reverse Words in a String II

Question:

Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.

The input string does not contain leading or trailing spaces and the words are always separated by a single space.

For example,
Given s = "the sky is blue",
return "blue is sky the".

Could you do it in-place without allocating extra space?

Solution:

public class Solution {
    public void reverseWords(char[] s) {

        //1.reverse the whole word
        reverse(s,0,s.length-1);
        //2.reverse each word
        int start = 0;
        for(int i=0;i<=s.length-1;i++){
            if(s[i]==' '){
                reverse(s,start,i-1);
                start=i+1;
            }
        }
        //0. if we have only one word
        reverse(s,start,s.length-1);
    }
    public void reverse(char[] s,int start, int end){
        while(start