Merge pull request #113 from justin-tse/master
Add the TypeScript code and docs for Chapter of Treepull/114/head
Yudong Jin
2 years ago
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GitHub
commit
02de01607b
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/**
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* File: binary_search_tree.ts
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* Created Time: 2022-12-14
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* Author: Justin (xiefahit@gmail.com)
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*/
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import { TreeNode } from '../module/TreeNode';
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import { printTree } from '../module/PrintUtil';
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/* 二叉搜索树 */
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let root: TreeNode | null;
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function BinarySearchTree(nums: number[]): void {
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nums.sort((a, b) => a - b); // 排序数组
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root = buildTree(nums, 0, nums.length - 1); // 构建二叉搜索树
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}
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/* 获取二叉树根结点 */
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function getRoot(): TreeNode | null {
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return root;
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}
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/* 构建二叉搜索树 */
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function buildTree(nums: number[], i: number, j: number): TreeNode | null {
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if (i > j) {
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return null;
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}
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// 将数组中间结点作为根结点
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let mid = Math.floor((i + j) / 2);
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let root = new TreeNode(nums[mid]);
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// 递归建立左子树和右子树
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root.left = buildTree(nums, i, mid - 1);
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root.right = buildTree(nums, mid + 1, j);
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return root;
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}
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/* 查找结点 */
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function search(num: number): TreeNode | null {
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let cur = root;
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// 循环查找，越过叶结点后跳出
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while (cur !== null) {
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if (cur.val < num) {
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cur = cur.right; // 目标结点在 root 的右子树中
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} else if (cur.val > num) {
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cur = cur.left; // 目标结点在 root 的左子树中
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} else {
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break; // 找到目标结点，跳出循环
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}
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}
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// 返回目标结点
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return cur;
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}
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/* 插入结点 */
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function insert(num: number): TreeNode | null {
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// 若树为空，直接提前返回
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if (root === null) {
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return null;
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}
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let cur = root,
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pre: TreeNode | null = null;
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// 循环查找，越过叶结点后跳出
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while (cur !== null) {
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if (cur.val === num) {
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return null; // 找到重复结点，直接返回
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}
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pre = cur;
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if (cur.val < num) {
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cur = cur.right as TreeNode; // 插入位置在 root 的右子树中
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} else {
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cur = cur.left as TreeNode; // 插入位置在 root 的左子树中
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}
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}
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// 插入结点 val
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let node = new 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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return node;
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}
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/* 删除结点 */
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function remove(num: number): TreeNode | null {
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// 若树为空，直接提前返回
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if (root === null) {
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return null;
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}
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let cur = root,
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pre: TreeNode | null = null;
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// 循环查找，越过叶结点后跳出
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while (cur !== null) {
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// 找到待删除结点，跳出循环
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if (cur.val === num) {
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break;
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}
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pre = cur;
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if (cur.val < num) {
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cur = cur.right as TreeNode; // 待删除结点在 root 的右子树中
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} else {
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cur = cur.left as TreeNode; // 待删除结点在 root 的左子树中
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}
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}
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// 若无待删除结点，则直接返回
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if (cur === null) {
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return null;
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}
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// 子结点数量 = 0 or 1
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if (cur.left === null || cur.right === null) {
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// 当子结点数量 = 0 / 1 时， child = null / 该子结点
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let child = cur.left !== null ? cur.left : cur.right;
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// 删除结点 cur
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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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}
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}
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// 子结点数量 = 2
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else {
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// 获取中序遍历中 cur 的下一个结点
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let next = min(cur.right);
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let tmp = next!.val;
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// 递归删除结点 nex
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remove(next!.val);
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// 将 nex 的值复制给 cur
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cur.val = tmp;
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}
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return cur;
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}
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/* 获取最小结点 */
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function min(root: TreeNode | null): TreeNode | null {
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if (root === null) {
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return null;
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}
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// 循环访问左子结点，直到叶结点时为最小结点，跳出
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while (root.left !== null) {
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root = root.left;
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}
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return root;
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}
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/* Driver Code */
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/* 初始化二叉搜索树 */
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const nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
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BinarySearchTree(nums);
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console.log('\n初始化的二叉树为\n');
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printTree(getRoot());
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/* 查找结点 */
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let node = search(5);
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console.log('\n查找到的结点对象为 ' + node + '，结点值 = ' + node!.val);
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/* 插入结点 */
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node = insert(16);
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console.log('\n插入结点 16 后，二叉树为\n');
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printTree(getRoot());
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/* 删除结点 */
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remove(1);
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console.log('\n删除结点 1 后，二叉树为\n');
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printTree(getRoot());
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remove(2);
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console.log('\n删除结点 2 后，二叉树为\n');
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printTree(getRoot());
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remove(4);
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console.log('\n删除结点 4 后，二叉树为\n');
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printTree(getRoot());
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export {};
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@ -0,0 +1,35 @@
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/**
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* File: binary_tree.ts
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* Created Time: 2022-12-13
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* Author: Justin (xiefahit@gmail.com)
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*/
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import { TreeNode } from '../module/TreeNode';
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import { printTree } from '../module/PrintUtil';
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/* 初始化二叉树 */
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// 初始化结点
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let n1 = new TreeNode(1),
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n2 = new TreeNode(2),
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n3 = new TreeNode(3),
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n4 = new TreeNode(4),
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n5 = new TreeNode(5);
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// 构建引用指向（即指针）
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n1.left = n2;
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n1.right = n3;
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n2.left = n4;
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n2.right = n5;
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console.log('\n初始化二叉树\n');
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printTree(n1);
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/* 插入与删除结点 */
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const P = new TreeNode(0);
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// 在 n1 -> n2 中间插入结点 P
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n1.left = P;
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P.left = n2;
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console.log('\n插入结点 P 后\n');
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printTree(n1);
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// 删除结点 P
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n1.left = n2;
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console.log('\n删除结点 P 后\n');
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printTree(n1);
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/**
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* File: binary_tree_bfs.ts
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* Created Time: 2022-12-14
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* Author: Justin (xiefahit@gmail.com)
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*/
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import { type TreeNode } from '../module/TreeNode';
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import { arrToTree } from '../module/TreeNode';
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import { printTree } from '../module/PrintUtil';
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/* 层序遍历 */
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function hierOrder(root: TreeNode | null): number[] {
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// 初始化队列，加入根结点
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const queue = [root];
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// 初始化一个列表，用于保存遍历序列
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const list: number[] = [];
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while (queue.length) {
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let node = queue.shift() as TreeNode; // 队列出队
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list.push(node.val); // 保存结点
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if (node.left) {
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queue.push(node.left); // 左子结点入队
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}
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if (node.right) {
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queue.push(node.right); // 右子结点入队
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}
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}
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return list;
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}
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/* Driver Code */
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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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var root = arrToTree([1, 2, 3, 4, 5, 6, 7, null, null, null, null, null, null, null, null]);
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console.log('\n初始化二叉树\n');
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printTree(root);
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/* 层序遍历 */
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const list = hierOrder(root);
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console.log('\n层序遍历的结点打印序列 = ' + list);
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/**
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* File: binary_tree_dfs.ts
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* Created Time: 2022-12-14
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* Author: Justin (xiefahit@gmail.com)
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*/
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import { type TreeNode } from '../module/TreeNode';
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import { arrToTree } from '../module/TreeNode';
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import { printTree } from '../module/PrintUtil';
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// 初始化列表，用于存储遍历序列
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const list: number[] = [];
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/* 前序遍历 */
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function preOrder(root: TreeNode | null): void {
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if (root === null) {
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return;
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}
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// 访问优先级：根结点 -> 左子树 -> 右子树
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list.push(root.val);
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preOrder(root.left);
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preOrder(root.right);
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}
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/* 中序遍历 */
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function inOrder(root: TreeNode | null): void {
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if (root === null) {
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return;
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}
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// 访问优先级：左子树 -> 根结点 -> 右子树
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inOrder(root.left);
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list.push(root.val);
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inOrder(root.right);
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}
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/* 后序遍历 */
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function postOrder(root: TreeNode | null): void {
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if (root === null) {
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return;
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}
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// 访问优先级：左子树 -> 右子树 -> 根结点
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postOrder(root.left);
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postOrder(root.right);
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list.push(root.val);
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}
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/* Driver Code */
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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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const root = arrToTree([1, 2, 3, 4, 5, 6, 7, null, null, null, null, null, null, null, null]);
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console.log('\n初始化二叉树\n');
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printTree(root);
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/* 前序遍历 */
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list.length = 0;
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preOrder(root);
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console.log('\n前序遍历的结点打印序列 = ' + list);
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/* 中序遍历 */
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list.length = 0;
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inOrder(root);
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console.log('\n中序遍历的结点打印序列 = ' + list);
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/* 后序遍历 */
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list.length = 0;
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postOrder(root);
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console.log('\n后序遍历的结点打印序列 = ' + list);
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@ -0,0 +1,51 @@
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/*
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* File: TreeNode.ts
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* Created Time: 2022-12-13
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* Author: Justin (xiefahit@gmail.com)
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*/
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/**
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* Definition for a binary tree node.
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*/
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class TreeNode {
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val: number;
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left: TreeNode | null;
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right: TreeNode | null;
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constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
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this.val = val === undefined ? 0 : val; // 结点值
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this.left = left === undefined ? null : left; // 左子结点指针
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this.right = right === undefined ? null : right; // 右子结点指针
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}
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}
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/**
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* Generate a binary tree with an array
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* @param arr
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* @return
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*/
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function arrToTree(arr: (number | null)[]): TreeNode | null {
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if (arr.length === 0) {
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return null;
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}
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const root = new TreeNode(arr[0] as number);
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const queue = [root];
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let i = 1;
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while (queue.length) {
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let node = queue.shift() as TreeNode;
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if (arr[i] !== null) {
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node.left = new TreeNode(arr[i] as number);
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queue.push(node.left);
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}
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i++;
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if (arr[i] !== null) {
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node.right = new TreeNode(arr[i] as number);
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queue.push(node.right);
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}
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i++;
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}
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return root;
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}
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export { TreeNode, arrToTree };
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