diff --git a/.vscode/settings.json b/.vscode/settings.json index 808d888..3b2e1f6 100644 --- a/.vscode/settings.json +++ b/.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", diff --git a/README.md b/README.md index 47d043c..0d2edfd 100644 --- a/README.md +++ b/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 - LintCode 70. 二叉树的层次遍历 II +- [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 + - LintCode 73. 前序遍历和中序遍历树构造二叉树 + ## 链表 - [合并K个排序链表](src/list/merge-k-sorted-lists.js) diff --git a/src/tree/construct-binary-tree-from-preorder-and-inorder-traversal.js b/src/tree/construct-binary-tree-from-preorder-and-inorder-traversal.js new file mode 100644 index 0000000..661cffc --- /dev/null +++ b/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 +} diff --git a/test/tree/construct-binary-tree-from-preorder-and-inorder-traversal.test.js b/test/tree/construct-binary-tree-from-preorder-and-inorder-traversal.test.js new file mode 100644 index 0000000..81eb30d --- /dev/null +++ b/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 }) +})