71 lines
1.8 KiB
Swift
71 lines
1.8 KiB
Swift
/**
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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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// Initialize the list for storing traversal sequences
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var list: [Int] = []
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/* Pre-order traversal */
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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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// Visit priority: root node -> left subtree -> right subtree
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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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/* In-order traversal */
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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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// Visit priority: left subtree -> root node -> right subtree
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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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/* Post-order traversal */
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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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// Visit priority: left subtree -> right subtree -> root node
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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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/* Initialize binary tree */
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// Use a specific function to convert an array into a binary tree
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let root = TreeNode.listToTree(arr: [1, 2, 3, 4, 5, 6, 7])!
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print("\nInitialize binary tree\n")
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PrintUtil.printTree(root: root)
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/* Pre-order traversal */
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list.removeAll()
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preOrder(root: root)
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print("\nSequence of nodes in pre-order traversal = \(list)")
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/* In-order traversal */
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list.removeAll()
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inOrder(root: root)
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print("\nInorder traversal node print sequence = \(list)")
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/* Post-order traversal */
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list.removeAll()
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postOrder(root: root)
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print("\nPostorder traversal node print sequence = \(list)")
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}
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}
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