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文章目录
  1. 题目介绍
  2. 复杂度
  3. 解题思路

Serialize and Deserialize Binary Tree

题目介绍

LeetCode 297. Serialize and Deserialize Binary Tree

复杂度

时间复杂度: O(n), 空间复杂度: O(n)

解题思路

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

class Codec {
private static let spliter = ","
private static let nullStr = "N"

func serialize(_ root: TreeNode?) -> String {
var str = ""
buildString(root, &str)
return str
}

private func buildString(_ root: TreeNode?, _ str: inout String) {
guard let root = root else {
str = str + Codec.nullStr + Codec.spliter
return
}
str = str + "\(root.val)" + Codec.spliter
buildString(root.left, &str)
buildString(root.right, &str)
}

func deserialize(_ data: String) -> TreeNode? {
var nodes: [String] = data.split(separator: Character(Codec.spliter)).map { String($0) }
return buildTree(&nodes)
}

private func buildTree(_ nodes: inout [String]) -> TreeNode? {
let val = nodes.removeFirst()
if val == Codec.nullStr {
return nil
}
let node = TreeNode(Int(val)!)
node.left = buildTree(&nodes)
node.right = buildTree(&nodes)
return node
}
}
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本文链接:http://yeziahehe.com/2020/05/06/SerializeAndDeserializeBinaryTree/

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