LeetCode（剑指 Offer）- 54. 二叉搜索树的第k大节点

题目链接：​​点击打开链接​​

题目大意：略

解题思路：略

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• 字节跳动

AC 代码

• Java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */

class Solution {

    int th;

    List<Integer> list = new ArrayList<>();

    public int kthLargest(TreeNode root, int k) {
        th = k;
        dfs(root);
        return list.get(k - 1);
    }

    void dfs(TreeNode node) {

        if (node == null || list.size() == th) {
            return;
        }

        dfs(node.right);
        list.add(node.val);
        dfs(node.left);
    }
}

• C++

class Solution {
public:
    int kthLargest(TreeNode* root, int k) {
        this->k = k;
        dfs(root);
        return res;
    }
private:
    int res, k;
    void dfs(TreeNode* root) {
        if(root == nullptr) return;
        dfs(root->right);
        if(k == 0) return;
        if(--k == 0) res = root->val;
        dfs(root->left);
    }
};