## Alpha

Palindromic Substrings
All Nodes Distance K in Binary Tree
Integer to Roman
Binary Tree Vertical Order Traversal
Diagonal Traverse

Find First and Last Position of Element in Sorted Array
Max Area of Island
Construct Binary Tree from Pre-order and In-order Traversal
Pour Water
ZigZag Conversion

## Beta

### EQ-1

Given a string, your task is to count how many palindromic substrings in this string.
The substrings with different start indexes or end indexes are counted as different substrings even they consist of same characters.

### EQ-2 *

We are given a binary tree (with root node `root`), a `target` node, and an integer value `K`.
Return a list of the values of all nodes that have a distance `K` from the `target` node. The answer can be returned in any order.

### EQ-3

Roman numerals are represented by seven different symbols: `I, V, X, L, C, D` and `M`.

### EQ-4

Given a binary tree, return the vertical order traversal of its nodes’ values. (ie, from top to bottom, column by column).
If two nodes are in the same row and column, the order should be from left to right.

### EQ-5

Given a matrix of M x N elements (M rows, N columns), return all elements of the matrix in diagonal order as shown in the below image.

### EQ-6

Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.
Your algorithm’s runtime complexity must be in the order of `O(log n)`.
If the target is not found in the array, return `[-1, -1]`.

### EQ-7

Given a non-empty 2D array grid of 0’s and 1’s, an island is a group of 1’s (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.
Find the maximum area of an island in the given 2D array. (If there is no island, the maximum area is 0.)

### EQ-8 *

Given preorder and inorder traversal of a tree, construct the binary tree.
`preorder = [3,9,20,15,7] inorder = [9,3,15,20,7]`

https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/solution/

### EQ-10

The string “PAYPALISHIRING” is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)

And then read line by line: “PAHNAPLSIIGYIR”

Feb 12, 2020
La Jolla, CA

## Omega

https://leetcode.com/