Reverse Words in a String

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

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

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.

思路：确定好每一个字符串，然后加入到ArrayList中，字符串由前后空格分隔

java代码：

1. public String reverseWords(String s) {
2. ArrayList<String> res = new ArrayList<String>();
3. int slen = s.length();
4. int index = 0;
5. while(true) {
6. while(index<slen&&s.charAt(index)==' ') index++;
7. if(index>=slen) break;
8. int start = index;
9. while(index<slen && s.charAt(index)!=' ') index++;
10. int end = index;
11. String str = s.substring(start,end);
12. res.add(str);
13. }
14. StringBuffer strBuffer = new StringBuffer();
15. if(res.size()==0) return "";
16. strBuffer.append(res.get(res.size()-1));
17. for(int i=res.size()-2;i>=0;i--) {
18. strBuffer.append(" ");
19. strBuffer.append(res.get(i));
20. }
21. return strBuffer.toString();
22. }