## Facebook Interview Questions

- 0of 0 votes
Find all words [A-Z] in a dictionary (about 1M words) that are made of a subset (in any order) of the chars in the input parameter [A-Z].

ex: input "ACRAT" (10 to 20 chars, up to 30 worst case)

matching words: "A", "CAR", "ACA", "ART", "RAC".

non-matching words: "BAR", "AAA"

follow up : the input is a list of words. Return a list of words that each

list is formed by exactly the characters in the input list.

For example: two lists {“DEBIT”, “CARD”} and{“BAD”, “CREDIT”}

are formed by the same exact group of characters.

- 0of 0 votes
Given a sorted list of integers, square the elements and give the output in sorted order.

- 0of 0 votes
Find the distance between the farthest two elements in a binary tree.

- 0of 0 votes
Given a string separated by a space like "123456 abc+efg" determine

the solution by mapping integers to letters like a:1, b:2, c:3, d:4, e:5, f:6.

The only operations allowed were + or -. So the calculated solution

that made the tests pass was 123+456 = 579.

- 0of 0 votes
How many subsets of a given array sum to zero?

- 0of 0 votes
Given numbers 1 through 52, take 5 unique numbers and determine

if the number 42 can be made using any combination of addition (+),

subtraction (-), multiplication (*), and division (/) on those 5 numbers

- 1of 1 vote
/* Intersection of two sorted interval lists, A=[(1,2), (5,7)..]

B=[(2,6)...] return [(5,6)..] */`import java.util.*; class Interval{ int start; int end; public Interval(int start, int end){ this.start = start; this.end = end; } } class Solution { public List<Interval> Intersection(Interval[] i1, Interval[] i2) {}`

- 0of 0 votes
* Given a string on length N. You can swap only the adjacent elements

and each element can be swapped atmost once.

Find the no of permutations of the string that can be generated after

performing the swaps as mentioned.

Ex –

string – “12345”

Ans = 8

Explanations- (All the permutations)

12345

21345

13245

12435

12354

21435

13254

21354

- 0of 0 votes
Given an array of n positive integers, find the number of subarrays

such that product of the elements of those subarrays are less than k.

For eg. Arr= {2, 3, 6} k=10

No of such subarrays= 4

- 1of 1 vote
Print the levels of a binary tree in reverse order using stack and recursion

`Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root). For example: Given binary tree 3 / \ 9 20 / \ 15 7 return its bottom-up level order traversal as: [ [15,7], [9,20], [3] ]`

public List<List<Integer>> levelOrderBottom(TreeNode root) {

}

- 0of 0 votes
given an array, find whether there exists 3 elements a,b,c in it such that a+b=c using efficient method.

- 0of 0 votes
You are provided a BST, which is corrupted. One of the nodes in it has 2 parents.

Let’s say those are parent 1 and parent 2. It is ensured that none

of these parents will be the ancestor of the other. Identify the node,

and remove the link of the wrong parent.

- 1of 1 vote
given an array of strings and characters, make the largest string possible.

The resultant string should be a combination of the strings given in the array.

The given array

of characters may contain repeated elements.

Example – Given char array – {a,a,b,c,d,d,e,c} and given strings

– {abba, aabc, de, cde} the

ans is aabccde

- 1of 1 vote
Given an adjacency matrix of a directed graph, find the number of cycles in the graph

- 0of 0 votes
Given K sorted (ascending) arrays. Write an iterator class that iterate over the arrays and returns the next element. Duplicate are allowed. What is the complexity to iterate the entire arrays? what is the complexity for each iteration?

Example:`arr1 = {1,2,3,4,7,9} arr2 = {3,5,6,8,10}`

The iterator should return:

`1,2,3,3,4,5,6,7,8,9,10`

Extension:

Don't return duplicates, so the above iterator should return:`1,2,3,4,5,6,7,8,9,10`

- 1of 1 vote
Given a binary tree that complies to the following rule:

The parent node value is always the the result of the AND operator of its children values.

You modify one of the LEAF nodes value (e.g. if it was 1 it is now 0). Write a function that fixes the tree

so it complies with the above rule.`// // 0 1 // / \ / \ // 1 0 =====> 1 1 // / \ / \ / \ / \ // 1 1 0 1 1 1 1 1 // // The parent node value is always children value's LOGICAL AND // & //`

- 0of 0 votes
Given an array of integers, return the index of the max value in this array.

Note:

If the max value appears more than once, the function should return one the indexes, but make it so that the next call will return different index.

Important: you are not allowed to store state between calls

Example: given this input array`// 0 -1 6 4 5 6 6 // | | | // 2,1/3 5,1/3 6,1/3`

Function signature:

`int getIndex(const std::vector<int>& numbers);`

Example output:

`2 5 6 5 2`

Extension:

What if you knew how many times the max value appears in the array, can you improve the function performance?

So using the given example array, the function signature is now:`int getIndex(const std::vector<int>& numbers, int maxCount);`

- 0of 0 votes
`Given an array of n * m matrix, and a moving matrix window (size k * k), move the window from top left to bottom right at each iteration, find the median number inside the window at each moving Can you do it better than brutal force method? void getMedian(int[][] matrix, int k){ print median } For matrix [ [1, 5, 3], [3, 2, 1], [4, 1, 9], ] The moving window size k = 2. At first the window is at the start of the array like this [ [|1, 5|, 3], [|3, 2|, 1], [4, 1, 9], ] ,get the median (2 + 3) / 2 = 2.5; then the window move one step forward. [ [1, |5, 3|], [3, |2, 1|], [4, 1, 9], ] ,get the median (2 + 3) / 2 = 2.5 then the window move one step forward again. [ [1, 5, 3], [|3, 2|, 1], [|4, 1|, 9], ] ,get the median (2 + 3) / 2 = 2.5 then the window move one step forward again. [ [1, 5, 3], [3, |2, 1|], [4, |1, 9|], ] ,get the median (1 + 2) / 2 = 1.5`

- 3of 3 votes
We are planning an orienteering game.

The aim of this game is to arrive at the goal (G) from the start (S) with the shortest distance.

However, the players have to pass all the checkpoints (@) on the map.

An orienteering map is to be given in the following format.

########

#@....G#

##.##@##

#..@..S#

#@.....#

########

In this problem, an orienteering map is to be given.

Calculate the minimum distance from the start to the goal with passing all the checkpoints.

Specification

* A map consists of 5 characters as following.

You can assume that the map does not contain any invalid characters and

the map has exactly one start symbol 'S' and exactly one goal symbol 'G'.

* 'S' means the orienteering start.

* 'G' means the orienteering goal.

* '@' means an orienteering checkpoint.

* '.' means an opened-block that players can pass.

* '#' means a closed-block that players cannot pass.

* It is allowed to move only by one step vertically or horizontally (up, down, left, or right) to the

next block.

Other types of movements, such as moving diagonally (left up, right up, left down and right down)

and skipping one or more blocks, are NOT permitted.

* You MUST NOT get out of the map.

* Distance is to be defined as the number of movements to the different blocks.

* You CAN pass opened-blocks, checkpoints, the start, and the goal more than once if necessary.

* You can assume that parameters satisfy following conditions.

* 1 <= width <= 100

* 1 <= height <= 100

* The maximum number of checkpoints is 18.

- 0of 0 votes
convert prefix to postfix expression

public String convert2postfix(String prefix){

}

- 1of 1 vote
Given an array of integers where each element points to the index of the next element how would you detect if there is a cycle in this array

can you do it without extra space

- 1of 1 vote
I get a chance to talk to Facebook software engineer during my android engineer interview. He asked me couple of question about native android like diff between views and fragment, mutable and immutable string, diff between string builder and string and a programming question convert int into words.

- 2of 2 votes
There is a maze of size m*n. You are sitting at (0,0). Another person is sitting in another cell. There are some cheeses placed in different cells with a cell value of 2. Some cells are blocked with a value of 1, thus you cannot pass it, while some cells are filled with 0, thus you can pass it.

You can move to left, right, up, down at each step. You have to collect all the pieces of cheese and then reach to Another Person cell. You need to return the minimum no. of steps required to do so.

Public int getShortest(int[][] maze, int[] anotherPersonCell){

}

- 1of 1 vote
We start with a list of Integers. We can remove a group of integers from the list if the all but one equals the remaining number. This removal operation can be performed in the remaining number of list until no more operations can be performed.

Write a function which can accept an array of integers, and return the minimal number of remaining integers from performing this operation.

Example [1, 3, 5, 6] -> remove 1, 5, 6 , because 1 + 5 = 6, thus only [3] left, so return 1

[48, 20, 1, 3, 4, 6, 9, 24] -> remove 3, 6, 9 , because 3 + 6 = 9, and remove 4, 20, 24, 48, because 4 + 20 + 24 + 48, thus only [1] left, so return 1

int left(int[] nums){

}

- 0of 0 votes
The numbers on a telephone keypad are arranged thus:

`1 2 3 4 5 6 7 8 9 0`

Starting from any digit, and choosing successive digits as a knight moves in chess, determine how many different paths can be formed of length n. There is no need to make a list of the paths, only to count them.

A knight moves two steps either horizontally or vertically followed by one step in the perpendicular direction; thus, from the digit 1 on the keypad a knight can move to digits 6 or 8, and from the digit 4 on the keypad a knight can move to digits 3, 9 or 0. A path may visit the same digit more than once.

Your task is to write a function that determines the number of paths of length n that a knight can trace on a keyboard starting from any digit .

public int findNumberOfPaths(int digit, int step){

- 0of 0 votes
How do I design a Payment Gateway system? What are the things to consider in this design ?

- 2of 2 votes
In Docker, building an image has dependencies. An image can only be built once

its dependency is built (If the dependency is from outside, then the image can

be built immediately).

Sometimes, engineers make mistakes by forming a cycle dependency of local images.

In this case, ignore the cycle and all the images depending on this cycle.

Input is vector of pair of images (image, its dependency).

Output the order of images to be built in order.

##Example:

```

Example 1:

{{"master", "ubuntu"}, {"numpy", "master"}, {"tensorflow", "numpy"}}

Output: master, numpy, tensorflow

Example 2:

{{"python", "numpy"}, {"numpy", "python"}, {"tensorflow", "ubuntu"}}

Output: tensorflow

Example 3:

{{"b", "c"}, {"c", "d"}, {"a", "b"}, {"d", "e"}, {"e","c"}, {"f", "g"}}

Ouput: f

- 0of 0 votes
There are n servers, reboot time is S0, S1..Sn-1

There are m tasks, the completion of the time required are T0, T1… Tm-1

How to assign tasks to each server makes the total time the shortest

- 1of 1 vote
If you are given 2 infinitely large integers in the form of strings, given the length of the string, find the product of the two integers.

- 0of 0 votes
How will you multiply two infinitely large integers.