Good morning! Here's our prompt for today.

Here's a fun one: let's say we have a 2D array matrix that is a size of m rows and n columns. It is initially prefilled with 0s and looks like the following:

1[[0, 0, 0, 0],
2 [0, 0, 0, 0],
3 [0, 0, 0, 0]]

We are then given a list of increment operations to be performed on the nested matrix array. An increment operation is exactly as it sounds-- it will dictate when to add 1 to a number in the matrix.

Each increment operation will consist of two numbers, a row and column value, that dictate to what extent the array's cells under that range should increment by 1.

For example, given the above matrix, if we get [1, 1] as an operation, it results in:

1[[1, 0, 0, 0],
2 [0, 0, 0, 0],
3 [0, 0, 0, 0]]

This is because we look at matrix[1][1], and look northwest to see what the "range" is. So what we've done is incremented all cells from matrix[0][0] to matrix[row][col] where 0 <= row < m, and 0 <= column < n.

If we then got another operation in the form of [2, 2], we'd get:

1[[2, 1, 0, 0],
2 [1, 1, 0, 0],
3 [0, 0, 0, 0]]

Can you write a method that returns the frequency of the max integer in the matrix? In the above example, it would be 1 (since 2 shows up just once).

Constraints

• Length of the array operations would be <= 100000
• The values of n and m <= 10000
• The values in operations will be in the range 1 and 10000
• Expected time complexity : O(n)
• Expected space complexity : O(1)

Try to solve this here or in Interactive Mode.

How do I practice this challenge?

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var assert = require('assert');

​

function maxFromOps(m, n, operations) {

  // fill this out

  return operations;

}

​

console.log(

  maxFromOps(4, 4, [

    [1, 1],

    [2, 2],

  ])

);

​

try {

  assert.equal(

    maxFromOps(4, 4, [

      [1, 1],

      [2, 2],

    ]),

    1

  );

​

  console.log(

    'PASSED: ' + 'Expect `maxFromOps(4, 4, [[1, 1], [2, 2]])` to return `1`'

  );

} catch (err) {

  console.log(err);

}

We'll now take you through what you need to know.

How do I use this guide?