add 222

fishercoder1534 · fishercoder1534 · commit 2214f62a27d0 · 2017-06-24T08:16:49.000+09:00
diff --git a/README.md b/README.md
@@ -341,7 +341,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |225|[Implement Stack using Queues](https://leetcode.com/problems/implement-stack-using-queues/)|[Solution](../master/src/main/java/com/fishercoder/solutions/ImplementStackUsingQueues.java)| O(n)|O(n) | Easy| Stack, Queue
 |224|[Basic Calculator](https://leetcode.com/problems/basic-calculator/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_224.java)| ?|? | Hard| 
 |223|[Rectangle Area](https://leetcode.com/problems/rectangle-area/)|[Solution](../master/src/main/java/com/fishercoder/solutions/RectangleArea.java)| O(1)|O(1) | Easy| 
-|222|[Count Complete Tree Nodes](https://leetcode.com/problems/count-complete-tree-nodes/)|[Solution](../master/src/main/java/com/fishercoder/solutions/CountCompleteTreeNodes.java)| O(?)|O(h) | Medium|
+|222|[Count Complete Tree Nodes](https://leetcode.com/problems/count-complete-tree-nodes/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_222.java)| O(?)|O(h) | Medium| Recursion
 |220|[Contains Duplicate III](https://leetcode.com/problems/contains-duplicate-iii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/ContainsDuplicateIII.java)| O(nlogn)|O(n) | Medium| TreeSet
 |219|[Contains Duplicate II](https://leetcode.com/problems/contains-duplicate-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/ContainsDuplicateII.java)| O(n)|O(n) | Easy| HashMap
 |218|[The Skyline Problem](https://leetcode.com/problems/the-skyline-problem/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_218.java)| O(n)|O(n) | Hard| TreeMap, Design
diff --git a/src/main/java/com/fishercoder/solutions/CountCompleteTreeNodes.java b/src/main/java/com/fishercoder/solutions/CountCompleteTreeNodes.java
diff --git a/src/main/java/com/fishercoder/solutions/_222.java b/src/main/java/com/fishercoder/solutions/_222.java
@@ -0,0 +1,49 @@
+package com.fishercoder.solutions;
+
+import com.fishercoder.common.classes.TreeNode;
+
+/**
+ * Given a complete binary tree, count the number of nodes.
+ * <p>
+ * Definition of a complete binary tree from Wikipedia:
+ * In a complete binary tree every level,
+ * except possibly the last, is completely filled,
+ * and all nodes in the last level are as far left as possible.
+ * It can have between 1 and 2h nodes inclusive at the last level h.
+ */
+public class _222 {
+
+    class Solution1 {
+        /**reference: https://discuss.leetcode.com/topic/21317/accepted-easy-understand-java-solution/2*/
+        public int countNodes(TreeNode root) {
+            int leftH = getLeftHeight(root);
+            int rightH = getRightHeight(root);
+            if (leftH == rightH) return (1 << leftH) - 1;
+            else return 1 + countNodes(root.left) + countNodes(root.right);
+        }
+
+        private int getRightHeight(TreeNode root) {
+            int height = 0;
+            while (root != null) {
+                root = root.right;
+                height++;
+            }
+            return height;
+        }
+
+        private int getLeftHeight(TreeNode root) {
+            int height = 0;
+            while (root != null) {
+                root = root.left;
+                height++;
+            }
+            return height;
+        }
+
+    }
+
+    public static void main(String...args) {
+        System.out.println(1 << 3);
+    }
+
+}
