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class Solution {
    func preorder(_ root: Node?) -> [Int] {
    	var stack = [root], ans = [Int]()
        while let node = stack.popLast(), let n = node {
            ans.append(n.val)
            stack += n.children.reversed()
        }
        return ans
    }
}

class Solution {
    func search(_ nums: [Int], _ target: Int) -> Int {
        var i = 0, j = nums.count-1
        while i <= j {
            let mid = i + (j-i)/2
            if nums[mid] == target { return mid }
            else if nums[mid] < target { i = mid+1
            } else { j = mid-1 }
        }
        return -1
    }
}

class Solution {
    func reverseString(_ s: inout [Character]) {
        s.reverse()
    }
}

class Solution {
    // iterative
    func preorderTraversal(_ root: TreeNode?) -> [Int] {
        var ans = [Int]()
        while let p = stack.popLast() {
            ans.append(p.val)
            if let r = p.right { stack.append(r) }
            if let l = p.left { stack.append(l) }
        }
        return ans
    }

    // recursive
    func preorderTraversal0(_ root: TreeNode?) -> [Int] {
        guard let root = root else { return [] }
        return [root.val] + preorderTraversal(root.left) + preorderTraversal(root.right)
    }
}

class Solution {
    func findMaxConsecutiveOnes(_ nums: [Int]) -> Int {
        return nums.split(separator: 0).map {$0.count}.max() ?? 0
    }
}