1. Write a program to print all paths in a binary tree where path-sum is equal to given number. This was asked in telephonic screening. 2. How will you serialize and de-serialize binary tree? 3. Find a median for a stream of numbers? Now, design a service which has this api to perform this operations? you have multiple streams now. 4. Give a start string "ball" , end string "John" and a dictionary that contains the some words. Find if you can conver "ball" to "john" by changing one char at a time, and using the words from the dictionary? How will you design large scale service doing the same?