select prefix and suffix of the array with maximum sum such that the sum of the length of the prefix and suffix is exactly K. code example
Example: build a prefix array cpp
void fillPrefixSum(int arr[], int n, int prefixSum[])
{
prefixSum[0] = arr[0];
// Adding present element
// with previous element
for (int i = 1; i < n; i++)
prefixSum[i] = prefixSum[i - 1] + arr[i];
}