SDE - 1

You are given a 2-dimensional array/list having N rows and M columns, which is filled with ones(1) and zeroes(0). 1 signifies land, and 0 signifies water.

A cell is said to be connected to another cell, if one cell lies immediately next to the other cell, in any of the eight directions (two vertical, two horizontal, and four diagonals).

A group of connected cells having value 1 is called an island. Your task is to find the number of such islands present in the matrix.

Aahad and Harshit always have fun by solving problems. Harshit took a sorted array consisting of distinct integers and rotated it clockwise by an unknown amount. For example, he took a sorted array = [1, 2, 3, 4, 5] and if he rotates it by 2, then the array becomes: [4, 5, 1, 2, 3].

After rotating a sorted array, Aahad needs to answer Q queries asked by Harshit, each of them is described by one integer Q[i]. which Harshit wanted him to search in the array. For each query, if he found it, he had to shout the index of the number, otherwise, he had to shout -1.

For each query, you have to complete the given method where 'key' denotes Q[i]. If the key exists in the array, return the index of the 'key', otherwise, return -1.

Note:

Can you solve each query in O(logN) ?

You are given a binary tree with ‘N’ nodes.

Your task is to find the “Maximum Path Sum” for any path.

Note :

1. A ‘path’ is a sequence of adjacent pair nodes with an edge between them in the binary tree.
2. The ‘path’ doesn’t need to pass through the root.
3. The ‘path sum’ is the sum of the node’s data in that path. 

Afzal has been working with an organization called 'Money Traders for the past few years. The organization is in the money trading business. His manager assigned him a task.

Given an array ’prices’ which denotes stock prices for ’n’ days, e.g., 'prices[ i ]' = price of the stock at ‘ith’ day, Find the stock's span for each day.

The span of the stock's price today is defined as the maximum number of consecutive days(starting from today and going backward) for which the price of the stock was less than today's price.

Example:

Input: ‘n’ = 7,  ‘prices’ = [100, 80, 60, 70, 60, 75, 85]

Output: [1, 1, 1, 2, 1, 4, 6]

Explanation: 
On the sixth day, when the stock price was 75, 

The span came out to be 4 because the last three prices(plus today) were less than the current or the sixth day's price.

Similarly, we can deduce the remaining results.

Note:

You don’t need to print anything. Just implement the given function

You are given an array of integers ‘coins’ denoting the denomination of coins and another array of integers ‘freq’ denoting the number of coins of each denomination.

You have to find the number of ways to make the sum ‘V’ by selecting some(or all) coins from the array.

The answer can be very large. So, return the answer modulo 1000000007.

For Example :

‘N’ = 3, ‘coins’ = {1, 2, 3}, ‘freq’ = {1, 1, 3}, ‘V’ = 6

For the given example, we can make six by using the following coins:
{1, 2, 3}
{3. 3}
Hence, the answer is 2.

You have been given a Binary Tree of integers. You are supposed to return the largest subtree sum in the given Binary Tree.

The subtree sum of a node is defined as the sum of all the node values formed by the subtree rooted at that node (including the node itself).

Example :

For the given binary tree:

Subtree with the largest sum is highlighted in the above image. The sum is (-2 + 4 + 7) = 9

Given a singly linked list of integers. Your task is to return the head of the reversed linked list.

For example:

The given linked list is 1 -> 2 -> 3 -> 4-> NULL. Then the reverse linked list is 4 -> 3 -> 2 -> 1 -> NULL and the head of the reversed linked list will be 4.

Follow Up :

Can you solve this problem in O(N) time and O(1) space complexity?

Given that integers are read from a data stream. Your task is to find the median of the elements read so far.

Median is the middle value in an ordered integer list. If the size of the list is even there is no middle value. So the median is the floor of the average of the two middle values.

For example :

[2,3,4] - median is 3.
[2,3] - median is floor((2+3)/2) = 2.

Given 'k' sorted linked lists, each list is sorted in increasing order. You need to merge all these lists into one single sorted list. You need to return the head of the final linked list.

For example:

Input:
3
3
4 6 8
3
2 5 7 
2
1 9

Output:
1 2 4 5 6 7 8 9 

Explanation:
First list is: 4 -> 6 -> 8 -> NULL
Second list is: 2 -> 5 -> 7 -> NULL
Third list is: 1 -> 9 -> NULL
The final list would be: 1 -> 2 -> 4 -> 5 -> 6 -> 7 -> 8 -> 9 -> NULL