内容简介:Given inorder and postorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.
Given inorder and postorder traversal of a tree, construct the binary tree.
Note:
You may assume that duplicates do not exist in the tree.
For example, given
inorder = [9,3,15,20,7] postorder = [9,15,7,20,3] Return the following binary tree: 3 / \ 9 20 / \ 15 7
难度:medium
题目:给定二叉树中序及后序遍历,构造二叉树,注意二叉树中的结点不重复。
思路;分治。
- 从后序遍历数组中由后向前取结点r
- 在中序遍历中找到r的位置,并由此结点分成两部分,继续执行1.
Runtime: 4 ms, faster than 68.02% of Java online submissions for Construct Binary Tree from Inorder and Postorder Traversal.
Memory Usage: 37.6 MB, less than 42.45% of Java online submissions for Construct Binary Tree from Inorder and Postorder Traversal.
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { public TreeNode buildTree(int[] inorder, int[] postorder) { if (null == postorder || postorder.length < 1) { return null; } return buildTree(inorder, 0, inorder.length - 1, postorder, postorder.length - 1); } public TreeNode buildTree(int[] inorder, int start, int end, int[] postorder, int idx) { if (start > end || idx < 0) { return null; } TreeNode root = new TreeNode(postorder[idx]); int rIdx = start; for (; rIdx <= end; rIdx++) { if (inorder[rIdx] == postorder[idx]) { break; } } root.left = buildTree(inorder, start, rIdx - 1, postorder, idx - (end - rIdx) - 1); root.right = buildTree(inorder, rIdx + 1, end, postorder, idx - 1); return root; } }
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具体数学(英文版第2版)
[美] Ronald L. Graham、Donald E. Knuth、Oren Patashnik / 机械工业出版社 / 2002-8 / 49.00元
This book introduces the mathematics that supports advanced computer Programming and the analysis of algorithms. The primary aim of its well-known authors is to provide a solid and relevant base of ma......一起来看看 《具体数学(英文版第2版)》 这本书的介绍吧!