Halo

Problem

Given a binary tree, return the zigzag level order traversal of its nodes’ values. (ie, from left to right, then right to left for the next level and alternate between).

Problem

Given a 2D board and a word, find if the word exists in the grid.

The word can be constructed from letters of sequentially adjacent cell, where “adjacent” cells are those horizontally or vertically neighboring. The same letter cell may not be used more than once.

Problem

Remove all elements from a linked list of integers that have value val.

Problem

Given two binary strings, return their sum (also a binary string).

The input strings are both non-empty and contains only characters 1 or 0.

Problem

Given an input string, reverse the string word by word.

Problem

Given two numbers, hour and minutes. Return the smaller angle (in degrees) formed between the hour and the minute hand.

Problem

Given a non-empty array of integers, return the k most frequent elements.

Problem

Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Note:

The solution set must not contain duplicate triplets.