Array -> Binary Search Tree

Array -> Binary Search Tree.swift

class Solution {
    func sortedArrayToBST(_ nums: [Int]) -> TreeNode? {
        return makeBST(nums, 0, nums.count - 1)
    }
    
    func makeBST(_ nums: [Int], _ start: Int, _ end: Int) -> TreeNode? {
        guard start <= end else { return nil }
        let mid = (start + end) / 2
        let node = TreeNode(nums[mid])
        node.left = makeBST(nums, start, mid - 1)
        node.right = makeBST(nums, mid + 1, end)
        return node
    }
}