Grokking 75: Top Coding Interview Questions
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Introduction to Sliding Window Pattern

You are given an array and a number K. Find the average of every block of K neighbouring elements.

[1, 3, 2, 6, -1, 4, 1, 8, 2]     K = 5

The direct approach is to take each starting index, add up the next five numbers, and divide. That is K additions for every one of the N starting points, so about O(N * K) work.

Now compare two neighbouring blocks. The block starting at index 0 holds 1, 3, 2, 6, -1. The block starting at index 1 holds 3, 2, 6, -1, 4. Four of the five numbers are the same. The direct approach adds those four again for no reason.

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A

aj

· 4 years ago

How is the complexity of brute force O(N*K)? N is the number of elements in input array - which in the example is 9. But the outer loop doesn't run 9 times does it? It will only run from 0 to arr.length - K i.e 4 times.

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J

Jake Bartles

· 4 years ago

is it possible to download this course for offline access?

Show 1 reply
D

Daniel Lim

· 4 years ago

What is the difference between these two ranges of for loops:

for i in range(len(arr)-K+1)

and

for i in range(K)

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O

ornella

· 4 years ago

Why windowSum is a float?

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S

srilu

· 4 years ago

In the Brute Force Python Solution why is "for i in range(len(arr)-K+1) " used instead of just " for i in range(K)" ? Aren't these two conditions the same thing?

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A

Adam Woolhether

· 4 years ago

I'll be writing my solutions in Go, anyone interested in reviewing with me?

J

joe

· 4 years ago

sum in the O(n * k) element JS solution wasn't initialized properly as 'let sum'

O

ornella

· 4 years ago

WindowStart is not in the for statement, so it shouldn't iterate, so how it is moving across the array?

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Priyanka Bhosale

Priyanka Bhosale

· 2 years ago

Is this course still available for me to access after my monthly subscription expires?