LeetCode: 700 Search in a Binary Search Tree

題目:

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.

只要是binary tree的通常都是用遞迴的方式處理
這題還算簡單
搜尋一樣值的節點之後返回

解法:

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func searchBST(root *TreeNode, val int) *TreeNode {
    if root == nil {
        return nil
    }
    
    if root.Val==val {
        return root
    } else if root.Val < val {
        return searchBST(root.Right, val)
    } else {
        return searchBST(root.Left, val)
    }
}

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