add subtree of another tree solution

Author: Tessa1217

subtree-of-another-tree/Tessa1217.java

@@ -0,0 +1,46 @@
+/**
+ * Definition for a binary tree node.
+ * 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;
+ *     }
+ * }
+ */
+class Solution {
+    public boolean isSubtree(TreeNode root, TreeNode subRoot) {
+        // subtree null일 경우
+        if (subRoot == null) {
+            return true;
+        }
+        // 이진 트리가 null일 경우
+        if (root == null) {
+            return false;
+        }
+        // subtree라면
+        if (isIdentical(root, subRoot)) {
+            return true;
+        }
+
+        return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot);
+
+    }
+
+    //  isIdentical(s,t)= s.val==t.val AND isIdentical(s.left,t.left) AND isIdentical(s.right,t.right)
+    private boolean isIdentical(TreeNode r, TreeNode s) {
+        if (r == null || s == null) {
+            return r == null && s == null;
+        }
+        if (r.val != s.val) {
+            return false;
+        }
+        return isIdentical(r.left, s.left) && isIdentical(r.right, s.right);
+    }
+}
+