exxtracted Treenode class to reuse; implemented Sub Tree checker reusing TreeComparison method

Author: ZapDos7

README.md

@@ -131,6 +131,7 @@
 
 ### Trees
 - [ ] [Same Tree](https://leetcode.com/problems/same-tree/)
+- [x] [Subtree of Another Tree](https://leetcode.com/problems/subtree-of-another-tree/)
 ### Heaps
 
 ## Multithreading
@@ -423,8 +424,6 @@
     - [ ] [Shortest Common Supersequence | Introduction & SCS Length](http://www.techiedelight.com/shortest-common-supersequence-introduction-scs-length/)
     - [ ] [Shortest Common Supersequence | Finding all SCS](http://www.techiedelight.com/shortest-common-supersequence-finding-scs/)
     - [ ] [Shortest Common Supersequence | Using LCS](http://www.techiedelight.com/shortest-common-supersequence-using-lcs/)
-- Tree
-    - [ ] [Subtree of Another Tree](https://leetcode.com/problems/subtree-of-another-tree/)
 
 - Binary Tree
     - [ ] [Binary Tree Maximum Path Sum](https://leetcode.com/problems/binary-tree-maximum-path-sum/)

src/dataStructures/trees/SubTreeChecker.java

@@ -0,0 +1,25 @@
+package dataStructures.trees;
+
+public class SubTreeChecker {
+    public static void main(String[] args) {
+        TreeNode p = new TreeNode(1, new TreeNode(2), new TreeNode(3));
+        TreeNode q = new TreeNode(2);
+
+        if (isSubtree(p, q)) {
+            System.out.println("Subtree!");
+        } else {
+            System.out.println("Not a subtree");
+        }
+    }
+
+    private static boolean isSubtree(TreeNode root, TreeNode subRoot) {
+        if (root == null) {
+            return subRoot == null;
+        }
+        if (TreeComparison.isSameTree(root, subRoot)) {
+            return true;
+        } else {
+            return TreeComparison.isSameTree(root.left, subRoot) || TreeComparison.isSameTree(root.right, subRoot);
+        }
+    }
+}

src/dataStructures/trees/TreeComparison.java

@@ -32,25 +32,4 @@ public static boolean isSameTree(TreeNode p, TreeNode q) {
 
         return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
     }
-
-
-    // Definition for a binary tree node.
-    public static class TreeNode {
-        int val;
-        TreeNode left;
-        TreeNode right;
-
-        TreeNode() {
-        }
-
-        TreeNode(int val) {
-            this.val = val;
-        }
-
-        TreeNode(int val, TreeNode left, TreeNode right) {
-            this.val = val;
-            this.left = left;
-            this.right = right;
-        }
-    }
 }

src/dataStructures/trees/TreeNode.java

@@ -0,0 +1,20 @@
+package dataStructures.trees;
+
+public class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+
+    TreeNode() {
+    }
+
+    TreeNode(int val) {
+        this.val = val;
+    }
+
+    TreeNode(int val, TreeNode left, TreeNode right) {
+        this.val = val;
+        this.left = left;
+        this.right = right;
+    }
+}