[leetcode] 235. Lowest Common Ancestor of a Binary Search Tree

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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 TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) 
 2     {
 3         if (root == NULL || NULL == p || NULL == q)
 4             return root;
 5         int max = p->val > q->val ? p->val : q->val;
 6         int min = p->val < q->val ? p->val : q->val;
 7         if (max < root->val) // p and q are left-subtree of root
 8             return lowestCommonAncestor(root->left, p ,q);
 9         else if (min > root->val)
10             return lowestCommonAncestor(root->right, p ,q);
11         else 
12             return root;
13     }

[leetcode] 235. Lowest Common Ancestor of a Binary Search Tree

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原文地址：http://www.cnblogs.com/ym65536/p/5469112.html