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/**
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* File: binary_tree_dfs.swift
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* Created Time: 2023-01-18
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* Author: nuomi1 (nuomi1@qq.com)
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*/
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import utils
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// 初始化列表，用于存储遍历序列
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var list: [Int] = []
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/* 前序遍历 */
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func preOrder(root: TreeNode?) {
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guard let root = root else {
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return
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}
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// 访问优先级：根节点 -> 左子树 -> 右子树
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list.append(root.val)
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preOrder(root: root.left)
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preOrder(root: root.right)
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}
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/* 中序遍历 */
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func inOrder(root: TreeNode?) {
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guard let root = root else {
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return
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}
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// 访问优先级：左子树 -> 根节点 -> 右子树
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inOrder(root: root.left)
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list.append(root.val)
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inOrder(root: root.right)
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}
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/* 后序遍历 */
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func postOrder(root: TreeNode?) {
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guard let root = root else {
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return
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}
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// 访问优先级：左子树 -> 右子树 -> 根节点
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postOrder(root: root.left)
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postOrder(root: root.right)
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list.append(root.val)
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}
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@main
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enum BinaryTreeDFS {
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/* Driver Code */
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static func main() {
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/* 初始化二叉树 */
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// 这里借助了一个从数组直接生成二叉树的函数
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let root = TreeNode.listToTree(arr: [1, 2, 3, 4, 5, 6, 7])!
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print("\n初始化二叉树\n")
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PrintUtil.printTree(root: root)
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/* 前序遍历 */
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list.removeAll()
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preOrder(root: root)
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print("\n前序遍历的节点打印序列 = \(list)")
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/* 中序遍历 */
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list.removeAll()
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inOrder(root: root)
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print("\n中序遍历的节点打印序列 = \(list)")
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/* 后序遍历 */
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list.removeAll()
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postOrder(root: root)
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print("\n后序遍历的节点打印序列 = \(list)")
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}
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}
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