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

标签：leetcode   c++   235   lowest common ancest   

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.

顺序二叉树中寻找两个叶节点的第一个公共父节点，查找，找到节点值大于等于第一个节点小于等于第二个节点的节点。（假设第一个节点值小于第二个节点值）。

AC代码：

class Solution
{
public:

    TreeNode* cal(TreeNode *root,TreeNode *p,TreeNode *q)
    {
        if(root->val>q->val)
            return cal(root->left,p,q);
        else if(root->val<p->val)
            return cal(root->right,p,q);
        else
            return root;
    }
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q)
    {
        if(p==q)
            return p;
        else
        {
            if(p->val>q->val)
                return cal(root,q,p);
            else
                return cal(root,p,q);
        }
    }
};

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

标签：leetcode   c++   235   lowest common ancest   

原文地址：http://blog.csdn.net/er_plough/article/details/47360481