add: 从前序与中序遍历序列构造二叉树

.vscode/settings.json

@@ -11,6 +11,7 @@
     "defanging",
     "dvdf",
     "eleetminicoworoep",
+    "inorder",
     "lcci",
     "lcof",
     "lcov",
@@ -20,6 +21,7 @@
     "mincost",
     "nums",
     "powx",
+    "preorder",
     "pwwkew",
     "subarray",
     "subarrays",

README.md

@@ -406,6 +406,11 @@ LeetCode 与 LintCode 解题记录。此为个人练习仓库，代码中对重
   - LeetCode 107. 二叉树的层次遍历 II <https://leetcode-cn.com/problems/binary-tree-level-order-traversal-ii/>
   - LintCode 70. 二叉树的层次遍历 II <https://www.lintcode.com/problem/binary-tree-level-order-traversal-ii/description>
 
+- [从前序与中序遍历序列构造二叉树](src/tree/construct-binary-tree-from-preorder-and-inorder-traversal.js)
+
+  - LeetCode 105. 从前序与中序遍历序列构造二叉树 <https://leetcode-cn.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/>
+  - LintCode 73. 前序遍历和中序遍历树构造二叉树 <https://www.lintcode.com/problem/construct-binary-tree-from-preorder-and-inorder-traversal/description>
+
 ## 链表
 
 - [合并K个排序链表](src/list/merge-k-sorted-lists.js)

src/tree/construct-binary-tree-from-preorder-and-inorder-traversal.js

@@ -0,0 +1,26 @@
+/**
+ * Definition for a binary tree node.
+ */
+function TreeNode (val) {
+  this.val = val
+  this.left = this.right = null
+}
+
+// 前序遍历：根左右
+// 中序遍历：左根右
+
+// 前序遍历知道根、中序遍历知道左边长度。
+
+/**
+ * @param {number[]} preorder
+ * @param {number[]} inorder
+ * @return {TreeNode}
+ */
+export const buildTree = function (preorder, inorder) {
+  if (inorder.length === 0) return null
+  const root = new TreeNode(preorder[0])
+  const index = inorder.indexOf(preorder[0])
+  root.left = buildTree(preorder.slice(1, index + 1), inorder.slice(0, index))
+  root.right = buildTree(preorder.slice(index + 1), inorder.slice(index + 1))
+  return root
+}

test/tree/construct-binary-tree-from-preorder-and-inorder-traversal.test.js

@@ -0,0 +1,5 @@
+import { buildTree } from '../../src/tree/construct-binary-tree-from-preorder-and-inorder-traversal'
+
+test('从前序与中序遍历序列构造二叉树', () => {
+  expect(buildTree([3, 9, 20, 15, 7], [9, 3, 15, 20, 7])).toEqual({ left: { left: null, right: null, val: 9 }, right: { left: { left: null, right: null, val: 15 }, right: { left: null, right: null, val: 7 }, val: 20 }, val: 3 })
+})