64 lines
1.6 KiB
Kotlin
64 lines
1.6 KiB
Kotlin
/**
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* File: binary_tree_dfs.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 chapter_tree
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import utils.TreeNode
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import utils.printTree
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// Initialize the list for storing traversal sequences
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var list = mutableListOf<Int>()
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/* Pre-order traversal */
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fun preOrder(root: TreeNode?) {
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if (root == null) return
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// Visit priority: root node -> left subtree -> right subtree
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list.add(root._val)
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preOrder(root.left)
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preOrder(root.right)
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}
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/* In-order traversal */
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fun inOrder(root: TreeNode?) {
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if (root == null) return
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// Visit priority: left subtree -> root node -> right subtree
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inOrder(root.left)
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list.add(root._val)
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inOrder(root.right)
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}
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/* Post-order traversal */
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fun postOrder(root: TreeNode?) {
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if (root == null) return
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// Visit priority: left subtree -> right subtree -> root node
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postOrder(root.left)
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postOrder(root.right)
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list.add(root._val)
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}
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/* Driver Code */
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fun main() {
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/* Initialize binary tree */
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// This is aided by a function that generates a binary tree from a list
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val root = TreeNode.listToTree(mutableListOf(1, 2, 3, 4, 5, 6, 7))
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println("\nInitialize binary tree\n")
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printTree(root)
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/* Pre-order traversal */
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list.clear()
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preOrder(root)
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println("\nPrint sequence of nodes in pre-order traversal = $list")
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/* In-order traversal */
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list.clear()
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inOrder(root)
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println("\nPrint sequence of nodes in in-order traversal = $list")
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/* Post-order traversal */
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list.clear()
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postOrder(root)
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println("\nPrint sequence of nodes in post-order traversal = $list")
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} |