157 lines
4.5 KiB
Kotlin
157 lines
4.5 KiB
Kotlin
/**
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* File: binary_search_tree.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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/* Binary search tree */
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class BinarySearchTree {
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// Initialize empty tree
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private var root: TreeNode? = null
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/* Get binary tree root node */
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fun getRoot(): TreeNode? {
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return root
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}
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/* Search node */
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fun search(num: Int): TreeNode? {
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var cur = root
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// Loop find, break after passing leaf nodes
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while (cur != null) {
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// Target node is in cur's right subtree
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cur = if (cur._val < num)
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cur.right
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// Target node is in cur's left subtree
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else if (cur._val > num)
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cur.left
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// Found target node, break loop
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else
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break
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}
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// Return target node
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return cur
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}
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/* Insert node */
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fun insert(num: Int) {
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// If tree is empty, initialize root node
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if (root == null) {
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root = TreeNode(num)
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return
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}
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var cur = root
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var pre: TreeNode? = null
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// Loop find, break after passing leaf nodes
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while (cur != null) {
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// Found duplicate node, thus return
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if (cur._val == num)
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return
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pre = cur
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// Insertion position is in cur's right subtree
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cur = if (cur._val < num)
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cur.right
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// Insertion position is in cur's left subtree
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else
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cur.left
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}
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// Insert node
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val node = TreeNode(num)
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if (pre?._val!! < num)
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pre.right = node
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else
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pre.left = node
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}
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/* Remove node */
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fun remove(num: Int) {
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// If tree is empty, return
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if (root == null)
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return
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var cur = root
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var pre: TreeNode? = null
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// Loop find, break after passing leaf nodes
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while (cur != null) {
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// Found node to be removed, break loop
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if (cur._val == num)
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break
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pre = cur
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// Node to be removed is in cur's right subtree
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cur = if (cur._val < num)
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cur.right
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// Node to be removed is in cur's left subtree
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else
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cur.left
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}
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// If no node to be removed, return
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if (cur == null)
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return
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// Number of child nodes = 0 or 1
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if (cur.left == null || cur.right == null) {
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// When the number of child nodes = 0/1, child = null/that child node
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val child = if (cur.left != null)
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cur.left
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else
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cur.right
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// Remove node cur
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if (cur != root) {
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if (pre!!.left == cur)
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pre.left = child
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else
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pre.right = child
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} else {
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// If the removed node is the root, reassign the root
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root = child
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}
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// Number of child nodes = 2
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} else {
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// Get the next node in in-order traversal of cur
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var tmp = cur.right
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while (tmp!!.left != null) {
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tmp = tmp.left
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}
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// Recursively remove node tmp
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remove(tmp._val)
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// Replace cur with tmp
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cur._val = tmp._val
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}
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}
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}
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/* Driver Code */
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fun main() {
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/* Initialize binary search tree */
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val bst = BinarySearchTree()
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// Note that different insertion orders can result in various tree structures. This particular sequence creates a perfect binary tree
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val nums = intArrayOf(8, 4, 12, 2, 6, 10, 14, 1, 3, 5, 7, 9, 11, 13, 15)
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for (num in nums) {
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bst.insert(num)
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}
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println("\nInitialized binary tree is\n")
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printTree(bst.getRoot())
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/* Search node */
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val node = bst.search(7)
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println("Found node object $node, node value = ${node?._val}")
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/* Insert node */
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bst.insert(16)
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println("\nAfter inserting node 16, the binary tree is\n")
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printTree(bst.getRoot())
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/* Remove node */
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bst.remove(1)
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println("\nAfter removing node 1, the binary tree is\n")
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printTree(bst.getRoot())
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bst.remove(2)
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println("\nAfter removing node 2, the binary tree is\n")
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printTree(bst.getRoot())
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bst.remove(4)
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println("\nAfter removing node 4, the binary tree is\n")
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printTree(bst.getRoot())
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} |