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flexible size sliding window

Mysterious Macaque answered on July 28, 2022 Popularity 3/10 Helpfulness 7/10

answer flexible size sliding window

flexible size sliding window

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/*
    Flexible-Size Sliding Window
    We refer to the flexible-size sliding window technique as the two-pointers technique.
    We’ll take an example of this technique to better explain it too.

    Problem:
    Suppose we have n books aligned in a row.
    For each book, we know the number of minutes needed to read it.
    However, we only have k free minutes to read.
    Also, we should read some consecutive books from the row.
    In other words, we can choose a range from the books in the row and read them.
    Of course, the condition is that the sum of time needed to read the books must not exceed k.
    Therefore, the problem asks us to find the maximum number of books we can read.
    Namely, we need to find a range from the array whose sum is at most k such that this range’s length is the maximum possible.
*/

/* 
  Naive approach 
  The complexity of this approach is O(n^2), 
  where n is the length of the array of books.
*/

let array = [2, 4, 1, 15, 6, 3, 2, 2, 1]
let minute = 8
let max = null

for (let i = 0; i < array.length; i++) {
    let sum = 0
    let count = 0
    let right = i

    while (sum + array[right] <= minute && right < array.length) {
        sum += array[right]
        right++
        count++
    }

    max = (max === null) ? count : (max < count) ? count : max
}

console.log(max)   // [Log]: 4  i.e. 3 + 2 + 2 + 1 <= 8


/*
	Sliding Window Algorithm with complexity O(n).
    The more precise time complexity of the algorithm below
    is (n-max)*max, where max is the maximum number of books we can read sequentially in k minutes.
*/
let array = [2, 4, 1, 15, 6, 3, 2, 2, 1]
let max = 1	  // assume that at least one readable book for k minute

for (let i = 0; i < array.length - max; i++) {
    let sum = array[i]
    let counter = 0

    while (sum <= minute) {
        sum += array[i + 1 + counter]
        counter++
    }

    if (max < counter) {
        max = counter
    }
}

console.log(max)	// [Log]: 4

Popularity 3/10 Helpfulness 7/10 Language javascript

Source: Grepper

Tags: javascript size sliding-window

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Contributed on Jul 28 2022

Mysterious Macaque

0 Answers Avg Quality 2/10

flexible size sliding window

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