CareerCup

April Google Interview 3/4
Maze
N,M array
Level 1 0,0 to N-1,M-1 => Path exsits?
Level 2 if path exists then print path
Level 3 if path exists then print min cost path
Level 4 O(nm log mn) using Priority Queue.

Write a function that receives string with decimal number (i.e. all characters are decimal digits) and prints the sum of all possible substring-numbers, example:
sum(“123”) = 123 + 12 + 23 + 1 + 2 + 3 = 167

Given N number of Strings, generate all combination of these String's characters, these Strings must be N long, and must contain only one number of char from each string.

example: "abc", "def", "ghi" --> adg, adh, adi, aeg ... cfg

Assume courses labeled by their index in an array. Given a list of pairs where the first element represents a prerequisite course required for the second course, derive an ordered list of courses.

For a given set of non-negative integers get the number of subsets that add up to a target value k.

Write a function to compute n^k. (don't forget negative exponents)

Imagine a horizontal corridor bounded by y = y1 and y = y2 lines on a 2D-plane. There are N sensors with centers (x, y) each of which operates in a range (r) on the plane . So, they cover some circular areas on the plane. See the figure below.

o            |
_____o___o__|____________ y = y1
		o	|OOO
__________oo|_____O______ y = y2
	O		|  O
_ _ _ _ _ _ | _ _ _ _ _ _
			|
	o O		|		o O
		O	|
			|
O			|
			|

The question is whether a path exist from x=-inf to x=+inf via corridor without being detected any radar.

Constraints:
1. You are free to move any direction only if you stay in the corridor.
2. You are free to go through corridor borders.
3. N sensors are given as list of (x, y, r) like [(1, 3, 2), (-1, -3, 4)]. x and y are signed integers. r is a unsigned integer.
4. y1 and y2 are integers.

My solution:
1. Create an intersection graph of N sensors by comparing them each other via Euclidean distance

(x1 - x2)^2 + (y1 - y2)^2 <= (r1 + r2)^2

2. If there is a path between y=y1 and y=y2 through intersected sensors, there do not exist any path from x=-inf to x=+inf. Otherwise, there do exist a path. So, I used BFS to search such a path.

Worst Case Complexity:
1. O(n^2)
2. O(V + E) = O(n + intersection_count)

Total: O(n^2)

My Best Case Optimization for Intersection Graph:
1. For each sensor, create two events for start and end of circles vertically. y = (y1 - r) and y = (y1 + r)
2. For each sensor, register those two events into an array.
3. Use a line sweep algorithm over 2, which is O(nlogn + intersection_count) and intersection_count may be n^2 at worst case.

I wonder if I should have had a better solution with the worst case < O(n^2).

You are given the length and time of occurrence of packet and Queues which process packets. Total processing time for a packet is equal to the length of packet plus the waiting time in queue. For eg lets say we have only one queue for now, and A packet of length 5 comes at t = 1, and another packet of length 4 comes at t = 3. Total processing time for first packet is 5( no waiting time as queue is empty at t = 1) and at t = 3, 2 units of first packet is processed and 3 units remaining so, for second packet 3 units will be waiting time in queue plus 4 units for its length. Total processing time for 2nd packet is 7 units. If there are multiple queues you can add new packet in any of the other queues. Given the time and length of all incoming packets, we need to find the minimum no. of queues required such that total processing time of each packet is less than 10 units. Maximum possible no. of queues are 5. If you require more than 5 queues print -1.


Test Cases Format: First Line contains the number N, the total no. of packets and N following line contains two numbers ti, li where li is length of packet coming at time = ti units.

Test case1:
2
2 7
5 8

Test Case 2:
3
1 3
2 3
3 5

Test Case 3:
3
1 5
2 4
3 8

Output:

Case1: 2
Case2: 1
Case3: 2

Consider the following time table of incoming packets:

time	packets-length
1	    8
2	    5
3	    2
4	    6

If you put the packet in queue with minimum time then this will lead to 3 queues:

t = 1:
q1: 8

t = 2:
q1: 7
q2: 5

t = 3:
q1: 6
q2: 4, 2

t = 4:
q1: 5
q2: 3, 2
q3: 6

But its output should be 2 queues:
1) 8 in queue 1
2) 5 in queue 2
3) 2 in queue 1
4) 6 in queue 2

Given a bar chart which the heights of bars are notated as an array of positive integers. Rectangles can be formed in areas covered by one or more bars. Find the largest rectangle.

FB On-site March

Q: Find number of Islands.
XXXOO
OOOXX
XXOOX
Return 3 islands.
1 1 1OO
OOO2 2
3 3OO 2


Followup: If the board is too big to fit in memory, how to get the number?

Given list of schedules for different flights in a month, determine maximum number of flights that can be in the air anytime in that month.
Input : list of schedules for flights.- spread over a month.

output: a number - maximum flights that can be in the air
Assumptions: 1. All the given times are in a specific timezone( like GMT).
2. Given Schedules can be any time in the month

Given a list of N threads detect a deadlock in the system.

A sample state of ‘a’:
[[2, NULL, 2, NULL],
[2, NULL, 2, NULL],
[NULL, NULL, NULL, NULL],
[NULL, NULL, NULL, NULL]]
FUNCTION foo()
FOR y = 0 to 3
FOR x = 0 to 3
IF a[x+1][y] != NULL
IF a[x+1][y] = a[x][y]:
a[x][y] := a[x][y]*2
a[x+1][y] := NULL
END IF
IF a[x][y] = NULL
a[x][y] := a[x+1][y]
a[x+1][y] := NULL
END IF
END IF
END FOR
END FOR
END FUNCTION

You have a 2 Dimensional Array.
1 2 3
4 5 6
7 8 9
Write code to generate all the 7 character strings without any duplicates starting from 4. You can move one block at a time and you can move either horizontally and diagonally. So for example, valid moves from 4 are 4 -> 1 and 4 -> 7. You can visit any node any number of times. so 4141414 is a valid string.

Given a string as input, return the list of all the patterns possible:

'1' : ['A', 'B', 'C'], 
'2' : ['D', 'E'],
'12' : ['X']
'3' : ['P', 'Q']

Example if input is '123', then output should be [ADP, ADQ, AEP, AEQ, BDP, BDQ, BEP, BEQ, CDP, CDQ, CEP, CEQ, XP, XQ]

Language : Java
Given a binary tree, print boundary nodes of the binary tree counter-clockwise starting from the root.
For example, boundary traversal of the following tree is “20 8 4 10 14 25 22”

20

8 22

4 12 25

10 14

Question 2: Given a number 'k', return the corresponding row, given the pattern:
k => output
0 => []
1 => ["0", "1", "8"]
2 => ["00", "11", "69", "96", "88"]
3 => ["000", "111", "101", "888", ...] // and so on ...

Question 1: Given an input of an array of string, verify if, turned 180 degrees, it is the "same".
For instance:
[1, 6, 0, 9, 1] => return true
[1, 7, 1] => return false

Dropbox

Grid Illumination: Given an NxN grid with an array of lamp coordinates.
Each lamp provides illumination to every square on their x axis,
every square on their y axis, and every square that lies in their diagonal
(think of a Queen in chess).
Given an array of query coordinates,
determine whether that point is illuminated or not. The catch is when checking a query all lamps adjacent to, or on,…

March 2018 Phone Interview FB
Calculate a moving average that considers the last N values.
Circular Queue (Interviewer didn't agree with the linked list queue that I suggested at first. Said the pointers took space)

Given two positive integers represented as linked lists, provide the sum of the numbers as a linked list.

1->2->3
4->5->6
-----------
5->7->9

1->2->3
4->5
-----------
1->6->8

4->5->6
7->8->9
-----------
1->2->4->5

A bus has to travel from A to B and the distance is d miles. There are many gas stations between A and B.
The bus has initially g gallon of gas in tank. 1 gallon of gas travels 1 mile.
Gas stations have inforamtion of remaining distance from station to destination b and max gas that can be filled from the station.
Find the minimum number of stops for bus without running out of gas ever.

eg: gas = 10 , distance = 20
gasStation[] = {{16,3}, {10, 7}, {14, 11},{11, 5}, {7, 6}}

o/p = 1
If bus stops at the stop{14,11} that is 14 miles away from destination and fills 11 gallon then it can reach destination with 1 gallon spare.
It can also stop as {16,3} and {10,7} but its 2 stops and at destination it runs out of gas.
Similarly {11, 5}, {7, 6} has 2 stops but has 1 gallon spare at destination.

Feb On-site Google

DP Problem. Given the length and width of a matrix, get the number of paths from bottom-left to bottom right.
You may only walk into those 3 directions ➡ (right) ↗ (upper-right) ↘ (lower-right) at each point.
Follow-up: optimize 2d DP to 1d DP of linear extra space.
Follow-up: what if some cells are blocked


System Design
Availability test/debug on distributed system. Discussed and drafted about failover, replication, NoSQL etc.
Interviewer seemed to be expecting more but time ran out.

Given a biased coin whose probability for Heads is 0.67 and Tails is 0.33, write an algorithm which will print the Heads and Tails with this probability.

Aisles contain products. Product is only going to be in one Aisle.

Product{

AisleID: string

ProductID: string

Price: float

}

Given Array<Product>, find the N highest price combinations. Combination is 1 product from each aisle. You can choose only one instance of each product.

So if you had two aisles

1: {$5,$4,$2}

and

2: {$6,$1)

And they asked for the 2 highest combos you would give $6,$5 and $6,$4

We have two sequences A and B consisting of integers, both of length N, and you would like them to be (strictly) increasing, i.e. for each K (0 ≤ K < N − 1), A[K] < A[K + 1] and B[K] < B[K + 1]. Thus, you need to modify the sequences, but the only manipulation you can perform is to swap an arbitrary element in sequence A with the corresponding element in sequence B. That is, both elements to be exchanged must occupy the same index position within each sequence.

For example, given A = [5, 3, 7, 7, 10] and B = [1, 6, 6, 9, 9], you can swap elements at positions 1 and 3, obtaining A = [5, 6, 7, 9, 10], B = [1, 3, 6, 7, 9].

Your goal is make both sequences increasing, using the smallest number of swaps.

Write a function:

public int minswaps(int[] A, int[] B);

that, given two zero-indexed arrays A, B of length N, containing integers, returns the minimum number of swapping operations required to make the given arrays increasing. If it is impossible to achieve the goal, return −1.

For example, given:

A[0] = 5 B[0] = 1
A[1] = 3 B[1] = 6
A[2] = 7 B[2] = 6
A[3] = 7 B[3] = 9
A[4] = 10 B[4] = 9
your function should return 2, as explained above.

Given:

A[0] = 5 B[0] = 2
A[1] = -3 B[1] = 6
A[2] = 6 B[2] = -5
A[3] = 4 B[3] = 1
A[4] = 8 B[4] = 0
your function should return −1, since you cannot perform operations that would make the sequences become increasing.

Given:

A[0] = 1 B[0] = -2
A[1] = 5 B[1] = 0
A[2] = 6 B[2] = 2
your function should return 0, since the sequences are already increasing.

Assume that:

N is an integer within the range [2..100,000];
each element of arrays A, B is an integer within the range [−1,000,000,000..1,000,000,000];
A and B have equal lengths.
Complexity O(N)

A and B are playing a perfect 8-9 game. The rules are pretty simple. At each point, you can either insert an 8 at the end of the previous number or a 9. one 8 and one 9 forms a pair. a 9 can only be inserted if there is an 8 which does not form a pair. Perfect solution is the one which has all its numbers in pair. Find out all the possible perfect outcomes of the game in lexicographic order.

Input-
Input 1: Max length of number

Output-
Your array must return an array of string s containing all possible outcomes.

Example 1:
Input: 4
Output: {"8899", "8989"}

Explanation: There can be only 2 possible outcomes out of 4 as nine must follow eight.

Example 2:
Input: 6
Output:{"888999","889899","889989","898899","898989"}

Explanation: The possible outcomes are 5.

Assume there is no software like google maps. you are given a map of world. Suppose you are somewhere in the hyderabad.
You will have to figure out all the paths from your location to Hyderabad airport.

I have given DFS approach. But the problem is that by doing DFS, a path can cross boundaries of Hyderabad and go so long away from Hyderabad
airport. DFS will take some much time. How to solve this problem?

Convert a string with digits into a literal representation of the number like: 1001 to one thousand one

We encode a string, s, by performing the following sequence of actions:

Replace each character with its ASCII value representation.
 Reverse the string.
For example, the table below shows the conversion from the string "Go VMWare" to the ASCII string "711113286778797114101":
	
//	Character	G	o		V	M	W	a 	r    e
//	ASCII Value	71 111  32  86  77  87  97  114  101
//
//	We then reverse the ASCII string to get the encoded string 101411797877682311117.
//
//	For reference, the characters in s are ASCII characters within the range 10 - 126 which include special characters.
//
//	Complete the decode function in the editor below. It has one parameter: 
//		encoded	- A reversed ASCII string denoting an encoded string s.
//		
//	The function must decode the encoded string and return the list of ways in which s can be decoded.

static Collection<String> decode(String encoded) {
}