1)Max Sum Subarray of size K- (sliding window)

 Given an array of integers Arr of size N and a number K. Return the maximum sum of a subarray of size K.

 

Example 1:

Input:
N = 4, K = 2
Arr = [100, 200, 300, 400]
Output:
700
Explanation:
Arr3  + Arr4 =700,
which is maximum.

 

Example 2:

Input:
N = 4, K = 4
Arr = [100, 200, 300, 400]
Output:
1000
Explanation:
Arr1 + Arr2 + Arr3  
+ Arr4 =1000,
which is maximum.

 

c++  implementation:

int maximumSumSubarray(int k, vector<int> &a , int n)
    {
        int i=0; int j=0;
        int s=0; int ms=0;
        
        while(j<n)
        {
            if(j-i+1<k)
            {
                s=s+a[j];
            }
            else if(j-i+1==k)
            {
                s=s+a[j];
                ms=s;
            }
            else
            {
                s=s-a[i];
                s=s+a[j];
                ms=max(s,ms);
                i++;
            }
        j++;
        }
        return ms;
    }

time complexity: O(n)
space complexity: O(1)