236-二叉树的最近公共祖先 ​

function lowestCommonAncestor(
  root: TreeNode | null,
  p: TreeNode | null,
  q: TreeNode | null,
): TreeNode | null {
  if (root === null) return null

  // 当前节点 root 如果就是 p 或 q，就返回 root
  if (root === p || root === q) return root

  const left = lowestCommonAncestor(root.left, p, q)
  const right = lowestCommonAncestor(root.right, p, q)

  if (left && right) return root

  return left || right
}

function lowestCommonAncestor(
  root: TreeNode | null,
  p: TreeNode | null,
  q: TreeNode | null,
): TreeNode | null {
  if (root === null) return null

  // 当前节点 root 如果就是 p 或 q，就返回 root
  if (root === p || root === q) return root

  const left = lowestCommonAncestor(root.left, p, q)
  const right = lowestCommonAncestor(root.right, p, q)

  if (left && right) return root

  return left || right
}