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Facebook Software Engineer Interview Question

I interviewed in Menlo Park, CA and was asked:
"How would you implement division without +, - or multiplication"
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Part of a Software Engineer Interview Review - one of 1,076 Facebook Interview Reviews

Answers & Comments

of 5

For integer division by 2 of unsigned int, use the shift operator. For other type of divisions, need to think more :)

- Anonymous on Dec 12, 2013
of 8

for division, a adding function needs to be built first
int add(int x, int y) {
    int a, b;
    do {
        a = x & y;
        b = x ^ y;
        x = a << 1;
        y = b;
    } while (a);
    return b;
the following part would be easy.

For the median searching problem, do not seek to load all the data into memory once for all. Do it in a smarter way. And keep in mind, the total number of integers are finite, so ask how much memory you can use, and do it with possibly multiple passes.

- Han Liu on Jan 5, 2014
of 3

How do you find the median among a billion numbers using 2 heaps? I thought the answer was related to the algorithms median of medians and selection.

- Merlin on Jan 13, 2014
of 3

I already saw the answer using 2 heaps but it loads all numbers in memory. http://stackoverflow.com/questions/10657503/find-running-median-from-a-stream-of-integers

- Merlin on Jan 13, 2014
of 1

// Flattening a linked list with an optional node assuming that
public class Node {

    private Object payload;
    private Node nextNode;
    private Node optionalNode;

    public Node(Object payload, Node nextNode, Node optionalNode) {
        this.payload = payload;
        this.nextNode = nextNode;
        this.optionalNode = optionalNode;

    public void setNextNode(Node nextNode) {
        this.nextNode = nextNode;

    public Object getPayload() {
        return payload;

    public Node getNextNode() {
        return nextNode;

    public Node getOptionalNode() {
        return optionalNode;

    public void setOptionalNode(Node optionalNode) {
        this.optionalNode = optionalNode;

// flatten a linkedlist with optional node
public static Node flattenLinkedList(Node head) {

        if (head == null) {
            return null;

        Node node = head;
        while (node != null) {
            if (node.getOptionalNode() != null) {
                Node newNext = flattenLinkedList(node.getOptionalNode());
            node = node.getNextNode();

        return head;


    // Given a head, return the last node of the list
    private static Node getLastNode(Node head) {
        if (head == null) return null;
        Node lastNode = head;
        while (head != null) {
            lastNode = head;
            head = head.getNextNode();
        return lastNode;

- ledger on May 10, 2014

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