leetcode------Reverse Words in a String

标题：	Reverse Words in a String
通过率：	14.8%
难度：	中等

Given an input string, reverse the string word by word.

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

Update (2015-02-12):
For C programmers: Try to solve it in-place in O(1) space.

click to show clarification.

Clarification:

 

• What constitutes a word?
  A sequence of non-space characters constitutes a word.
• Could the input string contain leading or trailing spaces?
  Yes. However, your reversed string should not contain leading or trailing spaces.
• How about multiple spaces between two words?
  Reduce them to a single space in the reversed string.

 

本本题思路比较清晰，就是遇到空格就是停止然后开始跳空格，最后进行迭代操作，具体代码如下：

 1 public class Solution {
 2     public String reverseWords(String s) {
 3            s = s.trim();
 4     return helper(s,0).toString();
 5         
 6     }
 7     private StringBuilder helper(String s, int index)
 8 {
 9     if(index>=s.length())
10         return new StringBuilder(); 
11     StringBuilder cur = new StringBuilder();
12     int lastIndex = index;
13     while(index < s.length() && s.charAt(index)!=' ')
14     {
15         cur.append(s.charAt(index++));
16     }
17     while(index < s.length() && s.charAt(index)==' ')
18         index++;
19     if(lastIndex == 0)
20         return helper(s,index).append(cur);
21     return helper(s,index).append(cur).append(' ');
22 }
23 }

 

转载于:https://www.cnblogs.com/pkuYang/p/4330871.html