solve problem

Author: delight010

subtree-of-another-tree/delight010.swift

@@ -0,0 +1,29 @@
+class Solution {
+    // Time O(M * N)
+    // Space O(N)
+    func isSubtree(_ root: TreeNode?, _ subRoot: TreeNode?) -> Bool {
+        if let root = root, let subRoot = subRoot {
+            if root.val == subRoot.val {
+                return dfs(root.left, subRoot: subRoot.left) && dfs(root.right, subRoot: subRoot.right) || isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot)
+            }
+            return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot)
+        }
+        
+        return false
+    }
+    
+    private func dfs(_ root: TreeNode?, subRoot: TreeNode?) -> Bool {
+        if root == nil && subRoot == nil {
+            return true
+        }
+        
+        if let root = root, let subRoot = subRoot {
+            if root.val == subRoot.val {
+                return dfs(root.left, subRoot: subRoot.left) && dfs(root.right, subRoot: subRoot.right)
+            }
+        }
+        
+        return false
+    }
+}
+