LeetCode Reverse Words in a String II

原题链接在这里：https://leetcode.com/problems/reverse-words-in-a-string-ii/

题目：

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?

Related problem: Rotate Array

题解：

类似Reverse Words in a String. input变成 char array.

先reverse 全部 char array. 从头往后走，遇到空格或者array尾部，就reverse中间的单词.

Time Compelxity: O(n). Space: O(1).

AC Java:

public class Solution {
public void reverseWords(char[] s) {
if(s == null || s.length == 0){
return;
}
reverse(s, 0, s.length-1);

int lo = 0;
for(int i = 1; i<=s.length; i++){
if(i == s.length || s[i] == ' '){
reverse(s, lo, i-1);
lo = i+1;
}
}
}

private void reverse(char [] s, int i, int j){
while(i < j){
swap(s, i++, j--);
}
}

private void swap(char [] s, int i , int j){
char temp = s[i];
s[i] = s[j];
s[j] = temp;
}
}