len_of_longest_subarray.py

def getLongestSubarray(a: [int], k: int) -> int:
    n = len(a) # size of the array.

    left, right = 0, 0 # 2 pointers
    Sum = a[0]
    maxLen = 0
    while right < n:
        # if sum > k, reduce the subarray from left
        # until sum becomes less or equal to k:
        while left <= right and Sum > k:
            Sum -= a[left]
            left += 1

        # if sum = k, update the maxLen i.e. answer:
        if Sum == k:
            maxLen = max(maxLen, right - left + 1)

        # Move forward the right pointer:
        right += 1
        if right < n: Sum += a[right]

    return maxLen


if __name__ == "__main__":
	a = [2, 3, 5, 1, 9]
	k = 10

	length = getLongestSubarray(a, k)
	print(f"The length of the longest subarray is: {length}")