235. Lowest Common Ancestor of a Binary Search Tree

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x),left(NULL),right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root,TreeNode* p,TreeNode* q) {
        if (p->val > q->val)    return lowestCommonAncestor(root,q,p);
        while (root != p && root != q) {
            if (p->val < root->val && q->val > root->val)
                return root;
            else if (p->val > root->val)
                root = root->right;
            else
                root = root->left;
        }
        return root;
    }
};