LeetCode_235Lowest Common Ancestor of a Binary Search Tree

Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.

According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”

    _______6______   /              \___2__          ___8__/     \        /      \0     _4       7       9     /  \     3   5

For example, the lowest common ancestor (LCA) of nodes 2 and 8 is 6. Another example is LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition.

如果root小于min(p, q)，那么LCA肯定在右子树上，那么递归
如果max(p, q)小于root，那么LCA肯定在左子树上，那么递归
如果root在pq之间，那么root肯定为LCA

 public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {           if(root == null) return null;           int min = p.val > q.val? q.val:p.val;           int max = p.val > q.val? p.val:q.val;           if(max < root.val){               return lowestCommonAncestor(root.left, p, q);           }           if(min > root.val){               return lowestCommonAncestor(root.right, p, q);           }           return root;        }