[swift] LeetCode 572. Subtree of Another Tree

Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node’s descendants. The tree s could also be considered as a subtree of itself.

Example 1:
Given tree s:

3
/ \
4 5
/ \
1 2
Given tree t:
4
/ \
1 2
Return true, because t has the same structure and node values with a subtree of s.
Example 2:
Given tree s:

3
/ \
4 5
/ \
1 2
/
0
Given tree t:
4
/ \
1 2
Return false.

func isSubtree(_ s: TreeNode?, _ t: TreeNode?) -> Bool {
    return ( maxDepth(s) >= maxDepth(t) )
        && ( isSameTree(s, t)
            || (s?.left != nil && isSubtree(s?.left, t))
            || (s?.right != nil && isSubtree(s?.right, t)) )
}

private func isSameTree(_ p: TreeNode?, _ q: TreeNode?) -> Bool {
    if let p = p, let q = q {
        return p.val == q.val && isSameTree(p.left, q.left) && isSameTree(p.right, q.right)
    } else {
        return p == nil && q == nil
    }
}

private func maxDepth(_ root: TreeNode?) -> Int {
    return root == nil ? 0 : 1 + max(maxDepth(root?.left), maxDepth(root?.right))
}

func isSubtree(_ s: TreeNode?, _ t: TreeNode?) -> Bool {

return ( maxDepth(s) >= maxDepth(t) )

&& ( isSameTree(s, t)

|| (s?.left != nil && isSubtree(s?.left, t))

|| (s?.right != nil && isSubtree(s?.right, t)) )

}

private func isSameTree(_ p: TreeNode?, _ q: TreeNode?) -> Bool {

if let p = p, let q = q {

return p.val == q.val && isSameTree(p.left, q.left) && isSameTree(p.right, q.right)

} else {

return p == nil && q == nil

}

private func maxDepth(_ root: TreeNode?) -> Int {

return root == nil ? 0 : 1 + max(maxDepth(root?.left), maxDepth(root?.right))

}

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