SlidingWindow.js

//Sliding Window Technique
//Technique to not fail the interview
//Take an array [1,2,3,4,5,6]
//if I needed to find all subarrays of length k = 3
//a brute force approach would cause me to iterate over two previous numbers again

//compute sum of every subarray of length l using a static sliding window

const arr = [1,2,3,4,5,6,7];
const k = 3;

const sumSubArr = function(arr, k) {

    let sum = arr.slice(0,3).reduce((acc, el) => acc + el, 0);
    const sumArr = [sum];

    for (let i = 0; i < arr.length; i++) {
        if (i + k >= arr.length) break;
        sum = sum - arr[i];
        sum = sum + arr[i + k];

        sumArr.push(sum);
    }

    return sumArr;


} 

/* console.log(sumSubArr(arr, k)); */

//Dynamic Sliding Window
//This sliding window technique involves starting of with a large window and then shrinking it

//Find the shortest subarray which has a sum greater than the target

const sample = [1,2,3,4,5,6,7,8,11];
const target = 11;

const smallestSubArr = function(arr, t) {

    let minLength = Infinity;
    let sum = 0;
    let start = 0;
    let end  = 0;

    while (end !== arr.length) {

        sum += arr[end];
        end++;

        while (start < end && sum >= target) {
            sum -= arr[start];
            start++;

            minLength = Math.min(minLength, end - start + 1);
        }
    }

    return minLength;

}

console.log(smallestSubArr(sample, target));