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lowest_common_ancestor_of_bt.cc
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lowest_common_ancestor_of_bt.cc
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/*
*https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/
*/
/*
*找一个bst中两个节点的最近公共祖先,要比一个二叉树找公共祖先容易,因为多了一个bst
* 条件,节点有序,如果两个值都小于根的值,则处理左子树;如果两个值都大于根,则处理
* 右子树;如果一个小于根植,一个大于根值,则根为最低公共祖先.
*/
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
#include <iostream>
using namespace std;
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 || p == NULL || q == NULL)
return NULL;
if(p == q)
return p;
if(p->val < root->val && q->val < root->val) //找左子树
return lowestCommonAncestor(root->left, p, q);
else if(p->val > root->val && q->val > root->val) //找右子树
return lowestCommonAncestor(root->right, p, q);
else
return root;
}
};