func ternarySearch(_ l: Int, _ r: Int, key: Int, in arr: [Int]) -> Int {
var left = l
var right = r
while left <= right {
let mid1 = left + (right - left) / 3
let mid2 = right - (right - left) / 3
if arr[mid1] == key { return mid1 }
if arr[mid2] == key { return mid2 }
if key < arr[mid1] {
right = mid1 - 1
} else if key > arr[mid2] {
left = mid2 + 1
} else {
left = mid1 + 1
right = mid2 - 1
}
}
return -1 // not found
}
func main() {
let arr = [1, 2, 8, 14, 15, 64, 78, 89, 99, 100, 110, 123]
let toSearch = 89
let index = ternarySearch(0, arr.count - 1, key: toSearch, in: arr)
if index != -1 {
print("Element found at index: \(index)")
} else {
print("Element not found.")
}
}
main()
/*
run:
Element found at index: 7
*/
