offer2-43

发布日期: 2023-05-11

完全二叉树是每一层（除最后一层外）都是完全填充（即，节点数达到最大，第 n 层有 2n-1 个节点）的，并且所有的节点都尽可能地集中在左侧。

设计一个用完全二叉树初始化的数据结构 CBTInserter，它支持以下几种操作：

CBTInserter(TreeNode root) 使用根节点为 root 的给定树初始化该数据结构；
CBTInserter.insert(int v) 向树中插入一个新节点，节点类型为 TreeNode，值为 v 。使树保持完全二叉树的状态，并返回插入的新节点的父节点的值；
CBTInserter.get_root() 将返回树的根节点。

示例 1：

输入：inputs = ["CBTInserter","insert","get_root"], inputs = [[[1]],[2],[]]
输出：[null,1,[1,2]]

示例 2：

输入：inputs = ["CBTInserter","insert","insert","get_root"], inputs = [[[1,2,3,4,5,6]],[7],[8],[]]
输出：[null,3,4,[1,2,3,4,5,6,7,8]]

提示：

//leetcode submit region begin(Prohibit modification and deletion)/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode() {} * TreeNode(int val) { this.val = val; } * TreeNode(int val, TreeNode left, TreeNode right) { * this.val = val; * this.left = left; * this.right = right; * } * } */class Solution { public List largestValues(TreeNode root) { List result = new ArrayList<>(); Queue nodeQ = new LinkedList<>(); if (root == null) { return result; } int nodeNum = 1; nodeQ.add(root); while (!nodeQ.isEmpty()) { int maxNum = Integer.MIN_VALUE; for (int i = 0; i < nodeNum; i++) { TreeNode node = nodeQ.poll(); if (node.val > maxNum) { maxNum = node.val; } if (node.left != null) { nodeQ.add(node.left); } if (node.right != null) { nodeQ.add(node.right); } } nodeNum = nodeQ.size(); result.add(maxNum); } return result; }}//leetcode submit region end(Prohibit modification and deletion)java
每个测试用例最多调用 CBTInserter.insert 操作 10000 次。
给定节点或插入节点的每个值都在 0 到 5000 之间。


//leetcode submit region begin(Prohibit modification and deletion)
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class CBTInserter {
    Queue<TreeNode> nodeQ;
    TreeNode root;

    public CBTInserter(TreeNode root) {
        nodeQ = new LinkedList<>();
        this.root = root;
        nodeQ.add(root);
        
        while (nodeQ.peek().left != null) {
            nodeQ.add(nodeQ.peek().left);
            if (nodeQ.peek().right != null) {
                nodeQ.add(nodeQ.poll().right);
            } else {
                break;
            }
        }
    }

    public int insert(int v) {
        TreeNode newNode = new TreeNode(v);
        int result = nodeQ.peek().val;
        if (nodeQ.peek().left == null) {
            nodeQ.peek().left = newNode;
        } else {
            nodeQ.poll().right = newNode;
        }
        nodeQ.add(newNode);
        return result;
    }

    public TreeNode get_root() {
        return this.root;
    }
}


/**
 * Your CBTInserter object will be instantiated and called as such:
 * CBTInserter obj = new CBTInserter(root);
 * int param_1 = obj.insert(v);
 * TreeNode param_2 = obj.get_root();
 */
//leetcode submit region end(Prohibit modification and deletion)