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* refactor: encode & decode Tree * style: build warning * feat: add Swift codes for array_representation_of_tree article
72 lines
2.1 KiB
Swift
72 lines
2.1 KiB
Swift
/**
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* File: TreeNode.swift
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* Created Time: 2023-01-02
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* Author: nuomi1 (nuomi1@qq.com)
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*/
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/* 二叉树节点类 */
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public class TreeNode {
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public var val: Int // 节点值
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public var height: Int // 节点高度
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public var left: TreeNode? // 左子节点引用
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public var right: TreeNode? // 右子节点引用
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/* 构造方法 */
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public init(x: Int) {
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val = x
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height = 0
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}
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// 序列化编码规则请参考：
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// https://www.hello-algo.com/chapter_tree/array_representation_of_tree/
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// 二叉树的数组表示：
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// [1, 2, 3, 4, nil, 6, 7, 8, 9, nil, nil, 12, nil, nil, 15]
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// 二叉树的链表表示：
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// /——— 15
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// /——— 7
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// /——— 3
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// | \——— 6
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// | \——— 12
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// ——— 1
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// \——— 2
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// | /——— 9
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// \——— 4
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// \——— 8
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/* 将列表反序列化为二叉树：递归 */
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private static func listToTreeDFS(arr: [Int?], i: Int) -> TreeNode? {
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if i < 0 || i >= arr.count || arr[i] == nil {
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return nil
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}
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let root = TreeNode(x: arr[i]!)
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root.left = listToTreeDFS(arr: arr, i: 2 * i + 1)
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root.right = listToTreeDFS(arr: arr, i: 2 * i + 2)
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return root
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}
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/* 将列表反序列化为二叉树 */
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public static func listToTree(arr: [Int?]) -> TreeNode? {
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listToTreeDFS(arr: arr, i: 0)
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}
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/* 将二叉树序列化为列表：递归 */
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private static func treeToListDFS(root: TreeNode?, i: Int, res: inout [Int?]) {
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if root == nil {
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return
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}
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while i >= res.count {
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res.append(nil)
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}
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res[i] = root?.val
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treeToListDFS(root: root?.left, i: 2 * i + 1, res: &res)
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treeToListDFS(root: root?.right, i: 2 * i + 2, res: &res)
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}
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/* 将二叉树序列化为列表 */
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public static func treeToList(root: TreeNode?) -> [Int?] {
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var res: [Int?] = []
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treeToListDFS(root: root, i: 0, res: &res)
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return res
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}
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}
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