Construct Binary Tree from Inorder and Preorder Traversal
Given two integer arrays preorder and inorder where preorder is the preorder traversal of a binary tree and inorder is the inorder traversal of the same tree, construct and return the binary tree.
/**
* @param {number[]} preorder
* @param {number[]} inorder
* @return {TreeNode}
*/
var buildTree = function(preorder, inorder) {
let hash = {};
inorder.forEach((e, i)=>{hash[e] = i});
let recur = function(start, end) {
if (start > end) return null;
let root = new TreeNode(preorder.shift());
root.left = recur(start, hash[root.val] - 1);
root.right = recur(hash[root.val] + 1, end);
return root;
}
return recur(0, inorder.length - 1);
};Related Problems
You are given the heads of two sorted linked lists list1 and list2.
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Return the head of the merged linked list.
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The "linked list" should use the same TreeNode class where the right child pointer points to the next node in the list and the left child pointer is always null.
The "linked list" should be in the same order as a pre-order traversal of the binary tree.
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You are given a 0-indexed array of unique strings words.
A palindrome pair is a pair of integers (i, j) such that:
0 <= i, j < words.length,
i != j, and
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Return an array of all the palindrome pairs of words.
You must write an algorithm with O(sum of words[i].length) runtime complexity.