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main.swift
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main.swift
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/**
297. Serialize and Deserialize Binary Tree
Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer,
or transmitted across a network connection link to be reconstructed later in the same or another computer environment.
Design an algorithm to serialize and deserialize a binary tree.
There is no restriction on how your serialization/deserialization algorithm should work.
You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.
Clarification: The input/output format is the same as how LeetCode serializes a binary tree.
You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.
Time complexity: O(n)
Space complexity: O(n)
*/
/**
* Definition for a binary tree node.
* 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 {
func serialize(_ root: TreeNode?) -> String {
var data = [String]()
dfs(root, &data)
return data.joined(separator: ",")
}
private func dfs(_ root: TreeNode?, _ data: inout [String]){
guard let root = root else {
data.append("#")
return
}
data.append("\(root.val)")
dfs(root.left, &data)
dfs(root.right, &data)
}
func deserialize(_ data: String) -> TreeNode? {
let items = data.components(separatedBy: ",")
guard
items.count > 0,
items[0] != "#"
else { return nil }
var index = 0
var root = TreeNode(Int(items[index])!)
decode(items, &index, root)
return root
}
private func decode(_ items: [String], _ index: inout Int, _ root: TreeNode?) {
if index + 1 >= items.count {
return
}
index += 1
if items[index] != "#" {
root?.left = TreeNode(Int(items[index])!)
decode(items, &index, root?.left)
}
if index + 1 >= items.count {
return
}
index += 1
if items[index] != "#" {
root?.right = TreeNode(Int(items[index])!)
decode(items, &index, root?.right)
}
}
}
// Your Codec object will be instantiated and called as such:
// var ser = Codec()
// var deser = Codec()
// deser.deserialize(ser.serialize(root))