reverse words in a string

fishercoder1534 · fishercoder1534 · commit 7feb35478798 · 2016-10-31T10:38:20.000-07:00
diff --git a/MEDIUM/src/medium/ReverseWordsinaString.java b/MEDIUM/src/medium/ReverseWordsinaString.java
@@ -0,0 +1,22 @@
+package medium;
+/**Given an input string, reverse the string word by word.
+
+For example,
+Given s = "the sky is blue",
+return "blue is sky the".*/
+public class ReverseWordsinaString {
+    public String reverseWords(String s) {
+        if(!s.contains(" ")) return s;//for cases like this: "a"
+        if(s.matches(" *")) return "";//for cases like this: " "
+        String[] words = s.split(" ");
+        StringBuilder sb = new StringBuilder();
+        for(int i = words.length-1; i >= 0; i--){
+            if(!words[i].equals("") && !words[i].equals(" ")){
+                sb.append(words[i]);
+                sb.append(" ");
+            }
+        }
+        sb.deleteCharAt(sb.length()-1);
+        return sb.toString();
+    }
+}
diff --git a/README.md b/README.md
@@ -38,6 +38,7 @@
 |165|[Compare Version Numbers](https://leetcode.com/problems/compare-version-numbers/)|[Solution](../../blob/master/EASY/src/easy/CompareVersionNumbers.java)| O(n)|O(1) | Easy|
 |162|[Find Peak Element](https://leetcode.com/problems/find-peak-element/)|[Solution](../../blob/master/MEDIUM/src/medium/FindPeakElement.java) | O(1) |O(logn)/O(n) | Binary Search|
 |155|[Min Stack](https://leetcode.com/problems/min-stack/)|[Solution](../../blob/master/EASY/src/easy/MinStack.java)| O(1)|O(n) | Easy| Stack
+|151|[Reverse Words in a String](https://leetcode.com/problems/reverse-words-in-a-string/)|[Solution](../../blob/master/MEDIUM/src/medium/ReverseWordsinaString.java)| O(n)|O(n) | Medium|
 |140|[Word Break II](https://leetcode.com/problems/word-break-ii/)|[Solution](../../blob/master/HARD/src/hard/WordBreakII.java)| ? |O(n^2) | Hard| Backtracking/DFS
 |139|[Word Break](https://leetcode.com/problems/word-break/)|[Solution](../../blob/master/MEDIUM/src/medium/WordBreak.java)| O(n^2)|O(n) | Medium| DP
 |133|[Clone Graph](https://leetcode.com/problems/clone-graph/)|[Solution](../../blob/master/MEDIUM/src/medium/CloneGraph.java)| O(n)|O(n) | Medium| HashMap, BFS 
