15_Maximum Points You Can Obtain from Cards

//link to the problem:https://leetcode.com/problems/maximum-points-you-can-obtain-from-cards/

//DSA sheet by Arsh Goyal: Problem 15


class Solution {
    public int maxScore(int[] cardPoints, int k) {
        int n=cardPoints.length,sum=0,max_sum=0;
        int start=0,end=(n-1-k);
        while(end<n){
           if(start==0)
           {
               for(int i=0;i<k;i++)
               sum=sum+cardPoints[n-i-1];
               max_sum=sum;
               start++;
               end++;
           }
            else
            {
                sum=sum-cardPoints[end]+cardPoints[start-1];
                if(sum>max_sum)
                    max_sum=sum;
                start++;
                end++;
            }
        }
        return max_sum;
    }
}