106.construct-binary-tree-from-inorder-and-postorder-traversal.js

/*
 * @lc app=leetcode id=106 lang=javascript
 *
 * [106] Construct Binary Tree from Inorder and Postorder Traversal
 *
 * https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/description/
 *
 * algorithms
 * Medium (46.98%)
 * Likes:    2073
 * Dislikes: 38
 * Total Accepted:    254.5K
 * Total Submissions: 531.7K
 * Testcase Example:  '[9,3,15,20,7]\n[9,15,7,20,3]'
 *
 * 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
 *
 *
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {number[]} inorder
 * @param {number[]} postorder
 * @return {TreeNode}
 */
var buildTree = function (inorder, postorder) {
    if (inorder.length < 1) return null;
    let root = new TreeNode();
    let rootVal = postorder[postorder.length - 1];
    root.val = rootVal;
    let rootIndex = inorder.indexOf(rootVal);
    root.left = buildTree(inorder.slice(0, rootIndex), postorder.slice(0, rootIndex));
    root.right = buildTree(inorder.slice(rootIndex + 1), postorder.slice(rootIndex, postorder.length - 1));
    return root;
};
// @lc code=end
// []\n[]
// [1]\n[1]