700-二叉搜索树中的搜索

LeetCode 700. Search in a Binary Search Tree

LeetCode-700

You are given the root of a binary search tree (BST) and an integer val.

Find the node in the BST that the node’s value equals val and return the subtree rooted with that node. If such a node does not exist, return null.

Input: root = [4,2,7,1,3], val = 2
Output: [2,1,3]

method: 递归

递归结束条件：如果节点为空，说明没找到，返回空节点；如果等于val，说明找到，也返回当前节点
单层逻辑：当前节点值比val大，往左子树找，比val小，往右子树找

TreeNode* searchBST(TreeNode* root, int val) {
    if (!root || root->val == val) return root;
    if (root->val > val) return searchBST(root->left, val);
    else return searchBST(root->right, val);
}