SDE - 1

You are given an array 'arr' of length 'n', consisting of integers.

A subarray is a contiguous segment of an array. In other words, a subarray can be formed by removing 0 or more integers from the beginning and 0 or more integers from the end of an array.

Find the sum of the subarray (including empty subarray) having maximum sum among all subarrays.

The sum of an empty subarray is 0.

Example :

Input: 'arr' = [1, 2, 7, -4, 3, 2, -10, 9, 1]

Output: 11

Explanation: The subarray yielding the maximum sum is [1, 2, 7, -4, 3, 2].

You have been given a board where there are '2' rows and 'N' columns. You have an infinite supply of 2x1 tiles, and you can place a tile in the following ways:

1. Horizontally as 1x2 tile
2. Vertically as 2x1 tile

Count the number of ways to tile the given board using the available tiles.

Note :

The number of ways might be large so output your answer modulo 10^9 + 7.

Here an example of tile and board for 'N' = 4 :

You are given an array “arr'' of integers. Your task is to find the contiguous subarray within the array which has the largest product of its elements. You have to report this maximum product.

An array c is a subarray of array d if c can be obtained from d by deletion of several elements from the beginning and several elements from the end.

For e.g.- The non-empty subarrays of an array [1,2,3] will be- [1],[2],[3],[1,2],[2,3],[1,2,3]. 

For Example:

If arr = {-3,4,5}.
All the possible non-empty contiguous subarrays of “arr” are {-3}, {4}, {5}, {-3,4}, {4,5} and {-3,4,5}.
The product of these subarrays are -3, 4, 5, -12, 20 and -60 respectively.
The maximum product is 20. Hence, the answer is 20.

Follow Up:

Can you solve this in linear time and constant space complexity?

Gary has N coins placed in a straight line. Some coins have head side up, and others have the tail side up.

Convention:

1 denotes the HEAD side is up. 
0 denotes the TAIL side is up. 

Now, Gary wants to obtain a maximum number of head-side up coins. He can perform at most one(possibly 0) flip in which he can flip the coins of a continuous interval (continuous subarray).

For example: In the given array (0 based indexing), { 1, 0, 0, 1, 0, 0, 1 }, we can obtain maximum head side up coins by flipping the coins in range 1 to 5. The array will thus become {1, 1, 1, 0, 1, 1, 1 }.

Return the maximum number of heads side up Gary can obtain.

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