// findMaxSumOfThree finds 'k' consecutive numbers with the largest sum in an array.
// Returns an optional tuple containing the maximum sum and the subsegment, or nil if invalid.
func findMaxSumOfThree(_ numbers: [Int], _ k: Int) -> (sum: Int, numbers: [Int])? {
// Validate input parameters: k must be positive and array count at least k
guard k > 0, numbers.count >= k else { return nil }
// Compute the sum of the initial window of size k
var currentSum = 0
for i in 0..<k {
currentSum += numbers[i]
}
var maxSum = currentSum
var maxStartIndex = 0
// Slide the window across the remaining elements:
// Subtract the element leaving on the left, add the element entering on the right.
for i in k..<numbers.count {
currentSum = currentSum - numbers[i - k] + numbers[i]
if currentSum > maxSum {
maxSum = currentSum
maxStartIndex = i - k + 1
}
}
// Extract the subsegment with the maximum sum safely
let maxNumbers = Array(numbers[maxStartIndex..<maxStartIndex + k])
return (maxSum, maxNumbers)
}
// Example usage:
let numbers = [4, 2, 0, 8, 7, 5, 1, 3, 9, 6]
let k = 3
if let result = findMaxSumOfThree(numbers, k) {
print("Largest sum: \(result.sum)")
// Format the numbers space-separated to match the example requirement
let formattedNumbers = result.numbers.map(String.init).joined(separator: " ")
print("Numbers: \(formattedNumbers)")
} else {
print("Invalid parameters or array too short.")
}
/*
run:
Largest sum: 20
Numbers: 8 7 5
*/
