LowestCommonAncestorOfABinaryTree

// Source: LeetCode-236: https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/submissions/
// Solution Ref: https://www.youtube.com/watch?v=WO1tfq2sbsI&ab_channel=CrackingFAANG
// Example Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1
// Output: 3

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public var val: Int
 *     public var left: TreeNode?
 *     public var right: TreeNode?
 *     public init(_ val: Int) {
 *         self.val = val
 *         self.left = nil
 *         self.right = nil
 *     }
 * }
 */

class Solution {
    func lowestCommonAncestor(_ root: TreeNode?, _ p: TreeNode?, _ q: TreeNode?) -> TreeNode? {

        guard let root = root, let p = p, let q = q else {
            return nil
        }

        if root.val == p.val || root.val == q.val {
            return root
        }

        let leftSearch = lowestCommonAncestor(root.left, p, q)
        let rightSearch = lowestCommonAncestor(root.right, p, q)

        if let foundLeft = leftSearch, let foundRight = rightSearch {
            return root
        }

        return leftSearch ?? rightSearch

    }
}