0572-subtree-of-another-tree.swift

/**
 * 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
 * }
 * }
 */
classSolution{
privatefunc areSameTrees(
 _ node1:TreeNode?,
 _ node2:TreeNode?
)->Bool{
 // if both are nil, they are same
if node1 ==nil && node2 ==nil{returntrue}

 // if anyone else is nil, they are not the same
guardlet node1 = node1 else{returnfalse}
guardlet node2 = node2 else{returnfalse}

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{returntrue}
guardlet root = root else{returnfalse}
guardlet subRoot = subRoot else{returnfalse}

 // Base case: Exactly same tree
ifareSameTrees(root, subRoot){returntrue}

 // Recursive
returnisSubtree(root.left, subRoot)
 || isSubtree(root.right, subRoot)
}
}