## Alpha

Burst Balloons
Valid Palindrome
Subdomain Visit Count
Min Stack
Lowest Common Ancestor of a Binary Tree

Most Common Word
Summary Ranges
Sliding Window Maximum
Design Hit Counter
Jump Game II

## Beta

### EQ-1

Given n balloons, indexed from `0` to `n-1`. Each balloon is painted with a number on it represented by array `nums`. You are asked to burst all the balloons. If the you burst balloon i you will get `nums[left] * nums[i] * nums[right]` coins. Here left and right are adjacent indices of `i`. After the burst, the `left` and `right` then becomes adjacent.
Find the maximum coins you can collect by bursting the balloons wisely.

### EQ-2

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
Note: For the purpose of this problem, we define empty string as valid palindrome.

### EQ-3

A website domain like “discuss.leetcode.com” consists of various subdomains. At the top level, we have “com”, at the next level, we have “leetcode.com”, and at the lowest level, “discuss.leetcode.com”. When we visit a domain like “discuss.leetcode.com”, we will also visit the parent domains “leetcode.com” and “com” implicitly.

Now, call a “count-paired domain” to be a count (representing the number of visits this domain received), followed by a space, followed by the address. An example of a count-paired domain might be “9001 discuss.leetcode.com”.

We are given a list cpdomains of count-paired domains. We would like a list of count-paired domains, (in the same format as the input, and in any order), that explicitly counts the number of visits to each subdomain.

### EQ-4

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

• `push(x)` – Push element x onto stack.
• `pop()` – Removes the element on top of the stack.
• `top()` – Get the top element.
• `getMin()` – Retrieve the minimum element in the stack.

### EQ-5

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself).”
Given the following binary tree: `root = [3,5,1,6,2,0,8,null,null,7,4]`

### EQ-6

Given a paragraph and a list of banned words, return the most frequent word that is not in the list of banned words. It is guaranteed there is at least one word that isn’t banned, and that the answer is unique.
Words in the list of banned words are given in lowercase, and free of punctuation. Words in the paragraph are not case sensitive. The answer is in lowercase.

### EQ-7

Given a sorted integer array without duplicates, return the summary of its ranges.
`Input: [0,1,2,4,5,7] Output: ["0->2","4->5","7"]`
`Explanation: 0,1,2 form a continuous range; 4,5 form a continuous range.`

### EQ-8

Given an array nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position. Return the max sliding window.

### EQ-9

Design a hit counter which counts the number of hits received in the past 5 minutes.
Each function accepts a timestamp parameter (in seconds granularity) and you may assume that calls are being made to the system in chronological order (ie, the timestamp is monotonically increasing). You may assume that the earliest timestamp starts at 1.
It is possible that several hits arrive roughly at the same time.

### EQ-10

Given an array of non-negative integers, you are initially positioned at the first index of the array.
Each element in the array represents your maximum jump length at that position.
Your goal is to reach the last index in the minimum number of jumps.

Feb 10, 2020
La Jolla, CA

## Omega

https://leetcode.com/