Issue # 3: IT training - current issues and challenges from leading companies

This week ends with a selection of tasks and questions that are often given during interviews on Facebook . Tasks chose different difficulty levels from “Easy” to “Hard”. The condition was again left in English. We’ll attach the solutions in a comment in a week. Good luck!

Questions:

1. Do you want to start the animation in half a second after the user clicks the button. What is the best way to do this?

2. The photo sharing application displays a system notification when a user receives a photo. Your application should display a photo when a user deletes a notification. Which of the following do you need to associate with the Notification object that you submit to Notification Manager?

Tasks:

1.

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.
For example, given nums = [0, 1, 0, 3, 12], after calling your function, numsshould be [1, 3, 12, 0, 0].
Note:
You must do this in-place without making a copy of the array.
Minimize the total number of operations.

2.

Given an array nums and a target value k, find the maximum length of a subarray that sums to k. If there isn't one, return 0 instead.

Note:
The sum of the entire nums array is guaranteed to fit within the 32-bit signed integer range.

Example 1 :

Given nums = [1, -1, 5, -2, 3], k = 3,
return 4. (because the subarray [1, -1, 5, -2] sumsto 3and is the longest)

Example 2 :

Given nums = [-2, -1, 2, 1], k = 1,
return 2. (because the subarray [-1, 2] sumsto 1and is the longest)

Follow Up:
Can you do it in O (n) time?

3.

Remove the minimum number of invalid parentheses in order to make the input string valid. Return all possible results.

Note : The input string may contain letters other than the parentheses (and).

Examples:
"()())()" -> ["()()()", "(())()"]
"(a)())()" -> ["(a)()()", "(a())()"]
")(" -> [""]