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LeetCode Legends!

L2 : 2D Arrays

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2D Arrays

What is a 2D Array?

This is when we have arrays as the elements of another array:

Example:

arr = [

[1, 2, 3],

[4, 5, 6],

[7, 8, 9]

]

Here we access row i and column j with arr[i][j]

Legends.add(u)

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Example Problem:

Number of Negative Numbers (Sorted)

Given a 2D Array of integers that is sorted in non-increasing order (from largest to smallest) in both the columns and the rows, write a function the counts the number of negative entries.

Example instance:

Answer here would be 5

Legends.add(u)

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Naive Approach: Brute Force

Iterate through every entry increasing your count when you come across a negative integer:

Runtime: Θ(r × c)

Memory: Θ(1)

Legends.add(u)

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A Faster Solution

Iterate through every entry increasing your count when you come across a negative integer:

Runtime: Θ(# of negative entries)

Memory: Θ(1)

Legends.add(u)