Title
because it is binary search tree can be determined phase interval
if the value of p and q are recursively right right of the current node
if the value of q and p are both at the left side of the current node left recursive
if Return the current node directly on both sides
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
if (root.val > p.val && root.val > q.val)
return lowestCommonAncestor(root.left,p,q);
if (root.val < p.val && root.val < q.val)
return lowestCommonAncestor(root.right,p,q);
return root;//p，q 在两侧
}