Leetcode 235. 二叉搜索树的最近公共祖先

/**
 * 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(root==NULL)return NULL;  
        // 要么在左子树，要么在右子树，要么就是根节点
        while(root){  
            if(p->val>root->val&&q->val>root->val)  
                root=root->right;  
            else if(p->val<root->val&&q->val<root->val)  
                root=root->left;  
            else return root;  
        } 
    }
};