## Interview Practice Extra 07 – Universal Value Binary Tree

Question Design an algorithm to verify that a tree is a universal value binary tree. Universal value binary tree means all value in that tree is the same. Solution There is two approach for this problem. One is with recursive function and another is with iterative function. For this problem, iterative function makes simpler answer. However,…

## Interview Practice Extra 06 – Vending Machine

Question This is an actual question I encountered in an Amazon phone interview in November 2013. You are going to design the money changing algorithm for a vending machine. That is, after any purchase, the machine makes change to users with a combination of coins. And the machine only have 3 types of coins: nickel…

## Interview Practice Extra 05 – Identify Prime Numbers

Question Write an algorithm to identify prime numbers from a list of numbers ranging 0-100. Solution The main question is actually to write a program to check if a number is prime. There are 4 situations. 1. If number is 0 or 1, it is not prime. 2. if the number is 2, it is…

## Interview Practice 19 – Fastest Way to Calculate Fibonacci Sequence

Question Construct an algorithm so that the Nth item of  Fibonacci Sequence can be found in the shortest time. Definition of Fibonacci Sequence is: = 0 , when n = 0 f(n) = 1 , when n = 1 = f(n-1) + f(n-2), when n > 1 Solution There are many solutions for this, the simplest way…

## Interview Practice 18 – Last Surviving Number in Loop

Consider Consider there is a list containing N numbers, and which formed a ring. That is, item n+1 is item 1. Construct an algorithm such that it traverses through the ring, and remove the Mth item. Repeat this process until there is only one number left in the ring and then output this number. For…

## Interview Practice 17 – Find The String Appeared Once

Question Given a string, write an algorithm to find the character inside that appeared only once. For example, the result for string “abaccdeff” is b. Solution We can use a hashtable to count the appearance times for each character. Then rescan the hashtable for the character that appeared only once. These two step take O(n)…

## Interview Practice Extra 03 – Verify Binary Tree with Same Value

Question Verify whether all nodes have the same value in a binary tree. Solution We can traverse the tree with our usual way, like depth-first or breadth-first algorithm. Then pass a value, probably the root value, to compare with the visiting node. Example # node structure class bst_node: value = None left = None right…

## Interview Practice Extra 02 – Duplicates in List

Question Write an algorithm to remove duplicated node from a linked list. Solution There are many ways to do it. For the first one, as the simplest one, we could use 2 loops to compare each element with all other elements. However, this takes forever: O(n²). The second way Reference http://www.geeksforgeeks.org/remove-duplicates-from-an-unsorted-linked-list/