Given three strings s1, s2, and s3, determine whether s3 can be formed by interleaving s1 and s2. An interleaving is a way of combining s1 and s2 such that the characters of s1 and s2 maintain their relative order in the final string.
You are given the root of a binary tree. Your task is to determine whether the tree is a valid binary search tree (BST). A binary search tree is valid if for every node in the tree, the value of all nodes in its left subtree are less than its own value, and the value of all nodes in its right subtree are greater than its own value.
You are given the root of a binary search tree (BST), but two nodes in the tree were swapped by mistake. Your task is to recover the tree by swapping the two nodes back, without changing the structure of the tree.
Given the root of a binary tree, your task is to return the level order traversal of its nodes’ values. This means you should traverse the tree level by level, from left to right at each level.
Given the root of a binary tree, your task is to return the zigzag level order traversal of its nodes’ values. This means you need to traverse the tree level by level, alternating between left to right and right to left on each level.
Given two integer arrays, preorder and inorder, representing the preorder and inorder traversals of a binary tree, your task is to reconstruct and return the binary tree. The values in the arrays are unique, and the preorder traversal provides the sequence in which nodes are visited before their children, while the inorder traversal provides the order in which nodes are visited between their children.
