Merge pull request neetcode-gh#1031 from Mahim1997/dev/572_swift

572. Subtree of Another Tree

swift/572-Subtree-of-Another-Tree.swift

@@ -0,0 +1,48 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ * public var val: Int
+ * public var left: TreeNode?
+ * public var right: TreeNode?
+ * public init() { self.val = 0; self.left = nil; self.right = nil; }
+ * public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ * public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ * self.val = val
+ * self.left = left
+ * self.right = right
+ * }
+ * }
+ */
+class Solution {
+ private func areSameTrees(
+ _ node1: TreeNode?, 
+ _ node2: TreeNode?
+ ) -> Bool {
+ // if both are nil, they are same
+ if node1 == nil && node2 == nil { return true }
+
+ // if anyone else is nil, they are not the same
+ guard let node1 = node1 else { return false }
+ guard let node2 = node2 else { return false }
+
+ return (
+ (node1.val == node2.val) &&
+ areSameTrees(node1.left, node2.left) &&
+ areSameTrees(node1.right, node2.right)
+ )
+ }
+
+ func isSubtree(_ root: TreeNode?, _ subRoot: TreeNode?) -> Bool {
+ // Base cases (both can be nil, just any one can't)
+ if root == nil && subRoot == nil { return true }
+ guard let root = root else { return false }
+ guard let subRoot = subRoot else { return false }
+
+ // Base case: Exactly same tree
+ if areSameTrees(root, subRoot) { return true }
+
+ // Recursive
+ return isSubtree(root.left, subRoot) 
+ || isSubtree(root.right, subRoot)
+ }
+}