SDE - 1

There are ‘N’ doors and ‘N’ people in a house. Each person and door has a unique ID ranging from 1 to ‘N’. A person can change the status of the door i.e, if the door is open then a person can close the door and vice versa. Initially, all the doors are closed and each person wants to change the status of all doors whose ID is a multiple of the ID of the person. You need to find out the final status of all the doors.

The answer should be given in a form of a binary string where ‘0’ represents the closed door and ‘1’ represents the open door. For example, the status “close open close” will form a binary string “010”.

A committee of mathematicians decided to remove every natural number which contains digit 9 such as 9, 19, 29, ... . Hence the new sequence of natural numbers will be: 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, ….

Given the natural number ‘N’, can you find the ‘N’th number in the new sequence formed after removing every integer that contains 9?

Note:

The sequence of natural numbers are integers that start from 1.

You are given a map of an island. Your task is to find the perimeter of the island. The map is represented by a binary grid where ‘0’ represents water, and ‘1’ represents the land.

Note:

There is only one island and water surrounding it. There are no lakes, i.e., all the water is connected. Each edge of the land is 1 unit.

For example:

You are given map = [[0, 0, 0, 0, 0],
                     [0, 0, 1, 0, 0],
                     [0, 1, 1, 1, 0],
                     [0, 0, 1, 0, 0]]

You are given the map as:

Here, it can be clearly seen the perimeter of the island is 12. Hence the answer is 12.

You are given an unsorted array/list 'ARR' of 'N' integers. Your task is to return the length of the longest consecutive sequence.

The consecutive sequence is in the form ['NUM', 'NUM' + 1, 'NUM' + 2, ..., 'NUM' + L] where 'NUM' is the starting integer of the sequence and 'L' + 1 is the length of the sequence.

Note:

If there are any duplicates in the given array we will count only one of them in the consecutive sequence.

For example-

For the given 'ARR' [9,5,4,9,10,10,6].

Output = 3
The longest consecutive sequence is [4,5,6].

Follow Up:

Can you solve this in O(N) time and O(N) space complexity?

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