题目描述

给定一个非空二叉搜索树（BST）和一个目标值 target，找到BST中与目标值最接近的整数值。注意，BST中的每个节点都包含一个唯一的整数值。

示例:

假设BST如下：

    4
   / \
  2   5
 / \
1   3

对于目标值 3.714286，BST中与它最接近的整数值是 4。

PHP 示例代码

class TreeNode {
    public $val;
    public $left;
    public $right;

    function __construct($val = 0, $left = null, $right = null) {
        $this->val = $val;
        $this->left = $left;
        $this->right = $right;
    }
}

function closestValue($root, $target) {
    $closest = $root->val;
    $diff = abs($root->val - $target);
    
    while ($root !== null) {
        $newDiff = abs($root->val - $target);
        if ($newDiff < $diff) {
            $diff = $newDiff;
            $closest = $root->val;
        }
        
        if ($root->val === $target) {
            break;
        } elseif ($root->val < $target) {
            $root = $root->right;
        } else {
            $root = $root->left;
        }
    }
    
    return $closest;
}

// 示例用法
$root = new TreeNode(4);
$root->left = new TreeNode(2);
$root->right = new TreeNode(5);
$root->left->left = new TreeNode(1);
$root->left->right = new TreeNode(3);

$target = 3.714286;
echo closestValue($root, $target);  // 输出 4

Python 示例代码

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def closestValue(root, target):
    closest = root.val
    diff = abs(root.val - target)
    
    while root:
        new_diff = abs(root.val - target)
        if new_diff < diff:
            diff = new_diff
            closest = root.val
        
        if root.val == target:
            break
        elif root.val < target:
            root = root.right
        else:
            root = root.left
    
    return closest

# 示例用法
root = TreeNode(4)
root.left = TreeNode(2)
root.right = TreeNode(5)
root.left.left = TreeNode(1)
root.left.right = TreeNode(3)

target = 3.714286
print(closestValue(root, target))  # 输出 4

JavaScript 示例代码

function TreeNode(val, left, right) {
    this.val = (val===undefined ? 0 : val)
    this.left = (left===undefined ? null : left)
    this.right = (right===undefined ? null : right)
}

function closestValue(root, target) {
    let closest = root.val;
    let diff = Math.abs(root.val - target);
    
    while (root) {
        let newDiff = Math.abs(root.val - target);
        if (newDiff < diff) {
            diff = newDiff;
            closest = root.val;
        }
        
        if (root.val === target) {
            break;
        } else if (root.val < target) {
            root = root.right;
        } else {
            root = root.left;
        }
    }
    
    return closest;
}

// 示例用法
const root = new TreeNode(4);
root.left = new TreeNode(2);
root.right = new TreeNode(5);
root.left.left = new TreeNode(1);
root.left.right = new TreeNode(3);

const target = 3.714286;
console.log(closestValue(root, target));  // 输出 4

码小课：在算法和数据结构的学习中，理解和实现二叉搜索树（BST）的相关操作是非常重要的。通过不断练习和解决实际问题，可以加深对BST特性的理解。码小课网站上有更多关于BST和其他算法的数据结构与算法相关内容，欢迎大家前往学习。