The question is a bit tricky, In programming terms we need to find sub-array such that you can draw maximum points

Sliding winndow algorithm is a useful technique whenever you need to find some substring or subarray. Here we need to find a subarray from the beginning and end

## Explanation:

example: cardPoints = [1,2,3,4,5,6,1] k = 3

- [1,2,3,4,5,6,1] –> start = [1,2,3], end = [], max = 6
- [1,2,3,4,5,6,1] –> start = [1,2], end = [1], max = 6
- [1,2,3,4,5,6,1] –> start = [1], end = [6, 1], max = 8
- [1,2,3,4,5,6,1] –> start = [], end = [5, 6, 1], max = 12

Here’s the algorithm

Create these variables *

`leftWindow = k - 1`

, wondering why leftWindow is k - 1? it’s because we need array indices values *`leftSum = 0`

`rightWindow = cardPoints.length - 1`

```
*
```

`rightSum = 0`

Now Loop through the card array k times and add each value to the leftSum

Let’s assume leftSum is the maxSum

`max = leftSum`

Start sliding the window while leftWindow is > 0 then decrease the leftSum and increase the rightSum. check whether leftSum + rightSum is greater than max

Here’s the solution

```
var maxScore = function(cardPoints, k) {
let leftW = k - 1,
leftSum = 0,
rightW = cardPoints.length - 1,
rightSum = 0;
for(let i = 0; i < k; i++) {
leftSum += cardPoints[i];
}
let max = leftSum;
while(leftW >= 0) {
leftSum -= cardPoints[leftW];
rightSum += cardPoints[rightW];
leftW--;
rightW--;
max = Math.max(max, leftSum + rightSum);
}
return max;
};
```