https://leetcode.com/problems/search-in-a-binary-search-tree/

1. Use binary search:

  1. //52 ms    34.8 MB
  3. /**
  4.  * Definition for a binary tree node.
  5.  * struct TreeNode {
  6.  *     int val;
  7.  *     TreeNode *left;
  8.  *     TreeNode *right;
  9.  *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
  10.  *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
  11.  *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
  12.  * };
  13.  */
  14. class Solution {
  15. public:
  16.     TreeNode* searchBST(TreeNode* root, int val) {
  17.         if(!root) return NULL;
  19.         if(root->val == val) return root;
  21.         if(val < root->val)
  22.             return searchBST(root->left, val);
  23.         else
  24.             return searchBST(root->right, val);
  25.     }
  26. };