Maximum Sum of Contiguous Subarray of Fixed Length

You are given an array of integers and a positive integer \(k\). Your task is to find the maximum sum of any contiguous subarray of length \(k\). If the input is invalid (for example, when \(k\) is non-positive or larger than the array length), then the output should be 0.

For example, if the array is [2, 1, 5, 1, 3, 2] and \(k = 3\), the contiguous subarrays of length 3 are [2, 1, 5], [1, 5, 1], [5, 1, 3], and [1, 3, 2] with sums 8, 7, 9, and 6 respectively. Hence, the answer is 9.

inputFormat

The input is read from standard input (stdin) and consists of three parts:

• The first line contains an integer \(n\), representing the number of elements in the array.
• The second line contains \(n\) space-separated integers, representing the array elements.
• The third line contains an integer \(k\), which specifies the length of the contiguous subarray.

outputFormat

Output a single integer to standard output (stdout): the maximum sum of any contiguous subarray of length \(k\). If the input is invalid (i.e., if \(n = 0\), \(k \leq 0\) or \(k > n\)), output 0.

6
2 1 5 1 3 2
3

9