# Month: February 2021

## Pseudo-Palindromic Paths in a Binary Tree

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.

## Palindrome Permutation

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.

## Combination Sum

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.

## Minimum Depth of Binary Tree

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.

## Find All Numbers Disappeared in an Array

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 HashMap

Design a HashMap without using any built-in hash table libraries. To be specific, your design should include these functions:

## Add Two Numbers

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.

## Merge Intervals

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.

## Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder traversal of a tree, construct the binary tree.

## Construct Binary Tree from Inorder and Postorder Traversal

Construct Binary Tree from Inorder and Postorder Traversal. Given inorder and postorder traversal of a tree, construct the binary tree.