/*
Demonstration of traversing an array from both ends
at the same time in idiomatic Swift.
We use the classic "two‑index" technique:
- left starts at index 0
- right starts at index arr.count - 1
Both move toward the center.
This approach is efficient (O(n)), simple, and widely used in
algorithms such as palindrome checks, partitioning, and pair searching.
*/
// ------------------------------------------------------------
// Function: traverseFromBothSides
// Purpose: Traverse an array from both ends simultaneously.
// ------------------------------------------------------------
func traverseFromBothSides(_ arr: [Int]) {
var left: Int = 0 // left index
var right: Int = arr.count - 1 // right index
// Move inward until the indices cross
while left <= right {
print("Left: \(arr[left]), Right: \(arr[right])")
left += 1
right -= 1
}
}
// ------------------------------------------------------------
// Main program
// ------------------------------------------------------------
let array: [Int] = [10, 20, 30, 40, 50, 60, 70, 80, 90]
print("Traversing from both sides:")
traverseFromBothSides(array)
/*
run:
Traversing from both sides:
Left: 10, Right: 90
Left: 20, Right: 80
Left: 30, Right: 70
Left: 40, Right: 60
Left: 50, Right: 50
*/
