hierholzer algorithm

You are given a list of airline tickets where tickets[i] = [fromi, toi] represent the departure and the arrival airports of one flight. Reconstruct the itinerary in order and return it. All of the tickets belong to a man who departs from “JFK”, thus, the itinerary must begin with “JFK”. If there are multiple valid itineraries, you should return the itinerary that has the smallest lexical order when read as a single string....

Given the root of a binary tree, construct a 0-indexed m x n string matrix res that represents a formatted layout of the tree. The formatted layout matrix should be constructed using the following rules: The height of the tree is height and the number of rows m should be equal to height + 1. The number of columns n should be equal to 2height+1 - 1. Place the root node in the middle of the top row (more formally, at location res[0][(n-1)/2])....