Netflix Interview Question for Senior Software Development Engineers

Country: United States
Interview Type: Written Test

Comment hidden because of low score. Click to expand.
of 0 vote

I would like to ask Interviewer whether he want to find out a loop for a given Spreadsheet or upon updating value of a cell. The complexity of the problem will differ in both the cases.

In case of doing this when updating value of a cell, I will follow this simple approach

For a given Cell value, Get all the referenced Node
Recursively try to find the referenced node. Dead end of the recursion would be no further reference to any cell. A reference back to the Start cell should tell us this is a loop.

Now someone can argue that it is possible to have a loop on the way, not to the start point. My answer would be, it will not be allowed when someone tried to edit value of C Cell.
E.g. A -> B ->C ->D ->C

If you really want to check loop in a given spread sheet, this is going to be little complex as one of the solution provided by thejediknight

- pc May 26, 2015 | Flag Reply
Comment hidden because of low score. Click to expand.
of 0 vote

This seems to work with the few tests I've done. I cheated a little and converted the letter indexed rows to just a number, but that wouldn't be too hard to swap back in if I had some real data to work with. I also assumed the "expressions" were just links to other cells, or null if there was no link.

import java.util.ArrayList;
import java.util.HashMap;

public class SpreadsheetProblem {
	public static boolean hasCycle(ArrayList<ArrayList<String>> spreadsheet, 
			HashMap<String, Boolean> visited, int c, int r) {
		System.out.println("looking at: " + c + ", " + r);
		String thisId = String.valueOf(c) + '-' + String.valueOf(r);
		if (visited.get(thisId) != null) {
			// this node has been visited before, we have found a cycle
			return true;
		ArrayList<String> thisColumn = spreadsheet.get(c);
		String thisNode = thisColumn.get(r);
		if (thisNode == null) {
			return false;
		visited.put(thisId, true);
		String[] edges = thisNode.split(" ");
		for (int i = 0; i < edges.length; i++) {
			String[] indexes = edges[i].split("-");
			int newC = Integer.parseInt(indexes[0]);
			int newR = Integer.parseInt(indexes[1]);
			if (hasCycle(spreadsheet, visited, newC, newR)) {
				return true;
		return false;		
	public static ArrayList<String> createRow(int c) {
		ArrayList<String> row = new ArrayList<String>();
		for (int i = 0;i < c; i++) {
		return row;
	public static ArrayList<ArrayList<String>> createSpreadsheet() {
		ArrayList<ArrayList<String>> spreadsheet = new ArrayList<ArrayList<String>>();
		ArrayList<String> r0 = createRow(10);
		r0.set(0, "3-0 3-3");
		r0.set(8, "1-2");
		ArrayList<String> r1 = createRow(10);
		r1.set(1, "3-3");
		ArrayList<String> r2 = createRow(10);
		ArrayList<String> r3 = createRow(10);
		r3.set(3, "0-0");
		r3.set(0, "2-0");
		return spreadsheet;
	public static void main(String[] args) {
		ArrayList<ArrayList<String>> spreadsheet = createSpreadsheet();
		HashMap<String, Boolean> visited = new HashMap<String, Boolean>();
		boolean hasCycle = false;		
		for (int c = 0; c < spreadsheet.size();c++) {
			ArrayList<String> thisCol = spreadsheet.get(c);
			for (int r = 0;r < spreadsheet.size();r++) {
				String thisNode = thisCol.get(r);
				if (thisNode != null) {
					if (hasCycle(spreadsheet, visited, c, r)) {
						hasCycle = true;
			if (hasCycle) break;
		System.out.println("Does the spreadsheet have a cycle? " +  hasCycle);	

- trevor June 12, 2015 | Flag Reply

Add a Comment

Writing Code? Surround your code with {{{ and }}} to preserve whitespace.


is a comprehensive book on getting a job at a top tech company, while focuses on dev interviews and does this for PMs.

Learn More


CareerCup's interview videos give you a real-life look at technical interviews. In these unscripted videos, watch how other candidates handle tough questions and how the interviewer thinks about their performance.

Learn More

Resume Review

Most engineers make critical mistakes on their resumes -- we can fix your resume with our custom resume review service. And, we use fellow engineers as our resume reviewers, so you can be sure that we "get" what you're saying.

Learn More

Mock Interviews

Our Mock Interviews will be conducted "in character" just like a real interview, and can focus on whatever topics you want. All our interviewers have worked for Microsoft, Google or Amazon, you know you'll get a true-to-life experience.

Learn More