Leetcode刷题记录——700. Search in a Binary Search Tree

  • 题目

Given the root node of a binary search tree (BST) and a value. You need to find the node in the BST that the node's value equals the given value. Return the subtree rooted with that node. If such node doesn't exist, you should return NULL.

For example, 

Given the tree:
        4
       / \
      2   7
     / \
    1   3

And the value to search: 2

You should return this subtree:

      2     
     / \   
    1   3

In the example above, if we want to search the value 5, since there is no node with value 5, we should return NULL.

Note that an empty tree is represented by NULL, therefore you would see the expected output (serialized tree format) as [], not null

  • 题目大意&解题思路

这道题其实就是给你一个二叉查找树,让你查找某一个值,如果找到返回节点的地址,如果没找到返回NULL。首先的思路肯定是用递归的方法。

/**
 * 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* searchBST(TreeNode* root, int val) {
        
        if( !root )     /*结点为空,返回NULL,没找到val*/
            return NULL;
        
        if( val == root->val  )
            return root;            
        else if( val > root->val )
            return searchBST(root->right,val);
        else
            return searchBST(root->left,val);
        
    }
};

Leetcode刷题记录——700. Search in a Binary Search Tree_第1张图片

你可能感兴趣的:(leetcode)