Given a binary tree where node values are digits from 1 to 9. A path in the binary tree is said to be pseudo-palindromic if at least one permutation of the node values in the path is a palindrome.
Write an efficient function that checks whether any permutation of an input string is a palindrome. You can assume the input string only contains lowercase letters.
Given an array of distinct integers candidates and a target integer target, return a list of all unique combinations of candidates where the chosen numbers sum to target. You may return the combinations in any order.
Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all the elements of [1, n] inclusive that do not appear in this array.
Design a HashMap without using any built-in hash table libraries. To be specific, your design should include these functions:
Given two number represent by LinkedList, calculate the sum of the numbers and store the result in a new LinkedList. Each node of the linked list is represented by single-digit and the head node is the most significant digit.
Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input.
Given preorder and inorder traversal of a tree, construct the binary tree.
Construct Binary Tree from Inorder and Postorder Traversal. Given inorder and postorder traversal of a tree, construct the binary tree.