Lowest Common Ancestor of a Binary Search Tree

一、题目内容

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.
二、代码实现

TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
if(root==NULL)
return NULL;
TreeNode* tmp=root;
while(1)
{
if((tmp->val<=p->val && tmp->val>=q->val)||(tmp->val>=p->val && tmp->val<=q->val))
return tmp;
else if(tmp->val<p->val && tmp->val<q->val)
tmp=tmp->right;
else if(tmp->val>p->val && tmp->val>q->val)
tmp=tmp->left;
}三、执行结果