added solution and test case for 151 (#148)

Author: ashmichheda

src/main/java/com/fishercoder/solutions/_151.java

@@ -27,4 +27,38 @@ public String reverseWords(String s) {
             return stringBuilder.substring(0, stringBuilder.length() - 1).toString();
         }
     }
+    public static class Solution2 {
+        public String reverseWords(String s) {
+            int len = s.length();
+            int i = 0;
+            int j = 0;
+            String result = "";
+            while (i < len) {
+
+                // index i keeps track of the spaces and ignores them if found
+                while (i < len && s.charAt(i) == ' ') {
+                    i++;
+                }
+                if (i == len) {
+                    break;
+                }
+                j = i + 1;
+
+                // index j keeps track of non-space characters and gives index of the first occurrence of space after a non-space character
+                while (j < len && s.charAt(j) != ' ') {
+                    j++;
+                }
+                // word found
+                String word = s.substring(i, j);
+                if(result.length() == 0) {
+                    result = word;
+                }
+                else {
+                    result = word + " "+ result;
+                }
+                i = j + 1;
+            }
+            return result;
+        }
+    }
 }

src/test/java/com/fishercoder/_151Test.java

@@ -8,11 +8,14 @@
 
 public class _151Test {
   private static _151.Solution1 solution1;
+  private static _151.Solution2 solution2;
   private static String s;
 
   @BeforeClass
-  public static void setup() {
+  public static void setup()
+  {
     solution1 = new _151.Solution1();
+    solution2 = new _151.Solution2();
   }
 
   @Test
@@ -38,4 +41,10 @@ public void test4() {
     s = "a b  c";
     assertEquals("c b a", solution1.reverseWords(s));
   }
+
+  @Test
+  public void test5() {
+    s = "  hello world  ";
+    assertEquals("world hello", solution2.reverseWords(s));
+  }
 }