Populating Next Right Pointers in Each Node

题目介绍

LeetCode 116. Populating Next Right Pointers in Each Node。

复杂度

时间复杂度: O(n), 空间复杂度: O(n)

解题思路

public class Node {
    public var val: Int
    public var left: Node?
    public var right: Node?
    public var next: Node?
    public init(_ val: Int) {
        self.val = val
        self.left = nil
        self.right = nil
        self.next = nil
    }
}

class Solution {
    func connect(_ root: Node?) -> Node? {
        dfs(root)
        return root
    }

    func dfs(_ root: Node?) {
        guard let root = root else {
            return
        }
        var left = root.left
        var right = root.right
        while left != nil {
            left!.next = right
            left = left?.right
            right = right?.left
        }
        dfs(root.left)
        dfs(root.right)
    }
}

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