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69 lines
2.1 KiB
69 lines
2.1 KiB
/**
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* File: TreeNode.kt
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* Created Time: 2024-01-25
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* Author: curtishd (1023632660@qq.com)
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*/
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package utils
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/* 二元樹節點類別 */
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/* 建構子 */
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class TreeNode(
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var _val: Int // 節點值
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) {
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var height: Int = 0 // 節點高度
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var left: TreeNode? = null // 左子節點引用
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var right: TreeNode? = null // 右子節點引用
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// 序列化編碼規則請參考：
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// https://www.hello-algo.com/chapter_tree/array_representation_of_tree/
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// 二元樹的陣列表示：
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// [1, 2, 3, 4, None, 6, 7, 8, 9, None, None, 12, None, None, 15]
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// 二元樹的鏈結串列表示：
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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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/* 將串列反序列化為二元樹：遞迴 */
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companion object {
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private fun listToTreeDFS(arr: MutableList<Int?>, i: Int): TreeNode? {
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if (i < 0 || i >= arr.size || arr[i] == null) {
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return null
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}
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val root = TreeNode(arr[i]!!)
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root.left = listToTreeDFS(arr, 2 * i + 1)
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root.right = listToTreeDFS(arr, 2 * i + 2)
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return root
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}
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/* 將串列反序列化為二元樹 */
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fun listToTree(arr: MutableList<Int?>): TreeNode? {
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return listToTreeDFS(arr, 0)
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}
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/* 將二元樹序列化為串列：遞迴 */
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private fun treeToListDFS(root: TreeNode?, i: Int, res: MutableList<Int?>) {
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if (root == null) return
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while (i >= res.size) {
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res.add(null)
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}
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res[i] = root._val
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treeToListDFS(root.left, 2 * i + 1, res)
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treeToListDFS(root.right, 2 * i + 2, res)
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}
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/* 將二元樹序列化為串列 */
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fun treeToList(root: TreeNode?): MutableList<Int?> {
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val res = mutableListOf<Int?>()
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treeToListDFS(root, 0, res)
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return res
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}
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}
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} |