hello-algo/codes/swift/chapter_tree/binary_search_tree.swift

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/**
* File: binary_search_tree.swift
* Created Time: 2023-01-26
* Author: nuomi1 (nuomi1@qq.com)
*/
import utils
/* */
class BinarySearchTree {
private var root: TreeNode?
init(nums: [Int]) {
let nums = nums.sorted() //
root = buildTree(nums: nums, i: 0, j: nums.count - 1) //
}
/* */
func getRoot() -> TreeNode? {
root
}
/* */
func buildTree(nums: [Int], i: Int, j: Int) -> TreeNode? {
if i > j {
return nil
}
//
let mid = (i + j) / 2
let root = TreeNode(x: nums[mid])
//
root.left = buildTree(nums: nums, i: i, j: mid - 1)
root.right = buildTree(nums: nums, i: mid + 1, j: j)
return root
}
/* */
func search(num: Int) -> TreeNode? {
var cur = root
//
while cur != nil {
// cur
if cur!.val < num {
cur = cur?.right
}
// cur
else if cur!.val > num {
cur = cur?.left
}
//
else {
break
}
}
//
return cur
}
/* */
func insert(num: Int) {
//
if root == nil {
return
}
var cur = root
var pre: TreeNode?
//
while cur != nil {
//
if cur!.val == num {
return
}
pre = cur
// cur
if cur!.val < num {
cur = cur?.right
}
// cur
else {
cur = cur?.left
}
}
//
let node = TreeNode(x: num)
if pre!.val < num {
pre?.right = node
} else {
pre?.left = node
}
}
/* */
@discardableResult
func remove(num: Int) {
//
if root == nil {
return
}
var cur = root
var pre: TreeNode?
//
while cur != nil {
//
if cur!.val == num {
break
}
pre = cur
// cur
if cur!.val < num {
cur = cur?.right
}
// cur
else {
cur = cur?.left
}
}
//
if cur == nil {
return
}
// = 0 or 1
if cur?.left == nil || cur?.right == nil {
// = 0 / 1 child = null /
let child = cur?.left != nil ? cur?.left : cur?.right
// cur
if cur !== root {
if pre?.left === cur {
pre?.left = child
} else {
pre?.right = child
}
} else {
//
root = child
}
}
// = 2
else {
// cur
var tmp = cur?.right
while tmp?.left != nil {
tmp = tmp?.left
}
// tmp
remove(num: tmp!.val)
// tmp cur
cur?.val = tmp!.val
}
}
}
@main
enum _BinarySearchTree {
/* Driver Code */
static func main() {
/* */
let nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
let bst = BinarySearchTree(nums: nums)
print("\n初始化的二叉树为\n")
PrintUtil.printTree(root: bst.getRoot())
/* */
var node = bst.search(num: 7)
print("\n查找到的节点对象为 \(node!),节点值 = \(node!.val)")
/* */
bst.insert(num: 16)
print("\n插入节点 16 后,二叉树为\n")
PrintUtil.printTree(root: bst.getRoot())
/* */
bst.remove(num: 1)
print("\n删除节点 1 后,二叉树为\n")
PrintUtil.printTree(root: bst.getRoot())
bst.remove(num: 2)
print("\n删除节点 2 后,二叉树为\n")
PrintUtil.printTree(root: bst.getRoot())
bst.remove(num: 4)
print("\n删除节点 4 后,二叉树为\n")
PrintUtil.printTree(root: bst.getRoot())
}
}