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Introduction

This pattern involves creating a window which can either be an array or number from one position to another. Depending on a certain condition, the window either increases or closes (and a new window is created). Very useful for keeping track of a subset of data in an array/string etc.


maxSubarraySum

Write a function called maxSubarraySum which accepts an array of integers and a number called n. The function should calculate the maximum sum of n consecutive elements in the array.

Time Complexity - O(N)

function maxSubarraySum(arr, num){
	let maxSum = 0;
	let tempSum = 0;
	if(arr.length < num){
		return null;
	}
	for(let i = 0; i < num; i++){
		maxSum += arr[i];
	}
	tempSum = maxSum;
	for(let i = num; i < arr.length; i++){
		tempSum = tempSum - arr[i - num] + arr[i];
		maxSum = Math.max(maxSum, tempSum);
	}
	return maxSum;
}
maxSubarraySum([1,2,5,2,8,1,5],2) // 10
maxSubarraySum([1,2,5,2,8,1,5],4) // 17
maxSubarraySum([4,2,1,6],1) // 6
maxSubarraySum([4,2,1,6,2],4) // 13
maxSubarraySum([],4) // null
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