Reverse Words in a String

 1 public class Solution {
 2     /**
 3      * @param s : A string
 4      * @return : A string
 5      */
 6     public String reverseWords(String s) {
 7         if (s == null || s.length() <= 1) return s;
 8 
 9         int start = 0;
10         List<Character> list = new ArrayList<Character>();
11         s = s.trim();
12 
13         for (int i = 0; i < s.length(); i++) {
14             if (!(s.charAt(i) == ‘ ‘ && list.get(list.size() - 1) == ‘ ‘)) {
15                 list.add(s.charAt(i));
16             }
17         }
18 
19         for (int i = 0; i < list.size(); i++) {
20             if (list.get(i) == ‘ ‘) {
21                 swap(list, start, i - 1);
22                 start = i + 1;
23             }
24         }
25 
26         swap(list, start, list.size() - 1);
27         swap(list, 0, list.size() - 1);
28 
29         StringBuilder sb = new StringBuilder();
30         for (int i = 0; i < list.size(); i++) {
31             sb.append(list.get(i));
32         }
33         return sb.toString();
34     }
35 
36     public void swap(List<Character> list, int i, int j) {
37         while (i < j) {
38             char temp = list.get(i);
39             list.set(i, list.get(j));
40             list.set(j, temp);
41             i++;
42             j--;
43         }
44     }
45 }