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You are given an integer 'N' denoting the size of a 'N' * 'N' matrix. Initially, each cell of the matrix is empty. You are also given an integer 'K' denoting the number of tasks. In each task, you are given two integers ('I','J') where 'I' represents the ith row, and 'J' represents the jth column of the matrix.

You have to perform each task in the given order. For each task, you have to place 0 in each cell of ith row and jth column. After completing all the tasks, you have to return an array of size 'K' where the nth element of the array is the number of empty cells in the matrix after the nth task.

For example: Consider an empty matrix of size 'N'*'N' where 'N' = 3. 

[[ 'NULL', 'NULL', 'NULL'] 
 [ 'NULL', 'NULL', 'NULL']
 [ 'NULL', 'NULL', 'NULL']]

Suppose the value of 'K' is 2, which means we have to perform 2 tasks. 

Task 1: (0, 0)
Matrix after placing 0 in each cell of 0th row and 0th column:
[[0, 0, 0] 
[ 0, 'NULL', 'NULL']
[ 0, 'NULL', 'NULL']]

The number of empty cells now: 4

Task 2: (1,0)
Matrix after placing 0 in each cell of 1st row and 0th column:
[[0, 0, 0] 
[ 0, 0, 0]
[ 0, 'NULL', 'NULL']]

The number of empty cells now: 2

Return the array [4,2]

Note:

1. We call a cell empty only if it does not contain any value.
2. Indexing is 0-based.  

the United Kingdom the currency is made up of pound (£) and pence (p). There are eight coins in general circulation:

1p, 2p, 5p, 10p, 20p, 50p, £1 (100p), and £2 (200p).
It is possible to make £2 in the following way:

1×£1 + 1×50p + 2×20p + 1×5p + 1×2p + 3×1p
How many different ways can £2 be made using any number of coins?

Find 2nd highest salary using 2 tables

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?