Lowest Common Ancestor of a Binary Search Tree-leetcode

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.

1、非递归

/** * 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!=nullptr&&p!=nullptr&&q!=nullptr){            TreeNode *temp=root;            while(true){                if(temp->val>q->val&&temp->val>p->val){                    temp=temp->left;                }else{                    if(temp->val<q->val&&temp->val<p->val){                        temp=temp->right;                    }else{                        return temp;                    }                }            }        }else{            return nullptr;        }            }};