SDE - 1

You are given two integers 'n' and 'm', the dimensions of a grid. The coordinates are from (0, 0) to (n - 1, m - 1).

The grid can only have values 0 and 1.

The value is 0 if there is water and 1 if there is land.

An island is a group of ‘1’s such that every ‘1’ has at least another ‘1’ sharing a common edge.

You are given an array 'queries' of size 'q'.

Each element in 'queries' contains two integers 'x' and 'y', referring to the coordinates in the grid.

Initially, the grid is filled with 0, which means only water and no land.

At each query, the value of 'grid' at (x, y) becomes 1, which means it becomes land.

Find out, after each query, the number of islands in the grid.

Example :

Input: 'n' = 3, 'm' = 4
'queries' = [[1, 1], [1, 2], [2, 3]]

Output: [1, 1, 2]

Explanation:

Initially, the grid was:
0 0 0 0
0 0 0 0
0 0 0 0

After query (1, 1):
0 0 0 0
0 1 0 0
0 0 0 0
There is one island having land (1, 1).

After query (1, 2):
0 0 0 0
0 1 1 0
0 0 0 0
Since (1, 1) and (1, 2) share a common edge, they form one island. So there is one island having lands (1, 1) and (1, 2).

After query (2, 3):
0 0 0 0
0 1 1 0
0 0 0 1
Now there are two islands, one having lands (1, 1) and (1, 2), and another having land (2, 3).

So the number of islands after each query is [1, 1, 2].

Pros and cons of indexing in a database. (Learn)

What is the difference between Write-back and write-through cache? Which one should be preferred? (Learn)

Given an array of numbers, find the maximum sum of any contiguous subarray of the array.

For example, given the array [34, -50, 42, 14, -5, 86], the maximum sum would be 137, since we would take elements 42, 14, -5, and 86.

Given the array [-5, -1, -8, -9], the maximum sum would be -1.

Follow up: Do this in O(N) time.

What is pickling? (Learn)

You are given a 2D board('N' rows and 'M' columns) of characters and a string 'word'.

Your task is to return true if the given word exists in the grid, else return false. The word can be constructed from letters of sequentially adjacent cells, where adjacent cells are horizontally or vertically neighboring.

Note:

The same letter cell should not be used more than once.

For Example:

For a given word “design” and the given 2D board 
[[q’, ‘v’, ‘m’, ‘h’],
 [‘d’, ‘e’, ‘s’, ‘i’],
 [‘d’, ‘g’, ‘f’, ‘g’],
 [‘e’, ‘c’, ‘p’, ‘n’]]

The word design can be formed by sequentially adjacent cells as shown by the highlighted color in the 2nd row and last column.

You are given an arbitrary binary tree, a node of the tree, and an integer 'K'. You need to find all such nodes which have a distance K from the given node and return the list of these nodes.

Distance between two nodes in a binary tree is defined as the number of connections/edges in the path between the two nodes.

Note:

1. A binary tree is a tree in which each node has at most two children. 
2. The given tree will be non-empty.
3. The given tree can have multiple nodes with the same value.
4. If there are no nodes in the tree which are at distance = K from the given node, return an empty list.
5. You can return the list of values of valid nodes in any order. For example if the valid nodes have values 1,2,3, then you can return {1,2,3} or {3,1,2} etc.

Example :

Consider this tree above. The target node is 5 and K = 3. The nodes at distance 1 from node 5 are {2}, nodes at distance 2 from node 5 are {1, 4} and nodes at distance 3 from node 5 are {6, 3}.