Restructure preparation section

algorithms/array.md

@@ -31,15 +31,10 @@ Arrays
   - [Source](http://blog.gainlo.co/index.php/2016/07/19/3sum/).
 - Given an array of numbers list out all quadruplets that sum to 0. Do so with a running time of less than O(n^4).
 - Given an array of integers, move all the zeroes to the end while preserving the order of the other elements. You have to do it in-place and are not allowed to use any extra storage.
-- Given a list of people, and a function `knows(a, b)` that returns `true`/`false` if person `a` knows the person `b`. Write a function that finds a VIP, which everybody knows and he doesn't know anybody else.
 - Given an array of integers, find the subarray with the largest sum. Can you do it in linear time.
   - Maximum subarray sum problem.
 - You have an array with the heights of an island (at point 1, point 2 etc) and you want to know how much water would remain on this island (without flowing away).
   - Trapping rain water question.
-- Given a sequence of tasks like `A, B, C` (means 3 different tasks), and a cold time, which means you need to wait for that much time to start the next same task, output the best task-finishing sequence.
-  - E.g. input: `AAABBB, 2`, output: `AB_AB_AB` ( `_` represents do nothing and wait)
-- You are given a list of dominoes. Determine if any two of those dominoes add up to `[6, 6]`.
-  - E.g. `[1, 4]` + `[5, 2]`).
 - Given an array containing only digits `0-9`, add one to the number and return the array.
   - E.g. Given `[1, 4, 2, 1]` which represents `1421`, return `[1, 4, 2, 2]` which represents `1422`.
 - Find the second maximum value in an array.