剑指offer-3.3-32.2

最新推荐文章于 2025-04-04 23:39:01 发布

Desperate_gh

最新推荐文章于 2025-04-04 23:39:01 发布

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分类专栏：剑指Offer 文章标签： leetcode

本文链接：https://blog.youkuaiyun.com/Desperate_gh/article/details/114304933

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/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<List<Integer>> levelOrder(TreeNode root) {
        List<List<Integer>> res = new LinkedList<List<Integer>>();
        if (root == null) {
            return res;
        }

        Queue<TreeNode> up = new LinkedList<TreeNode>();
        up.add(root);
        while (!up.isEmpty()) {
            Queue<TreeNode> down = new LinkedList<TreeNode>();
            List<Integer> temp = new LinkedList<Integer>();
            while (!up.isEmpty()) {
                TreeNode cur = up.poll();
                temp.add(cur.val);
                if (cur.left != null) {
                    down.add(cur.left);
                }
                if (cur.right != null) {
                    down.add(cur.right);
                }
            }
            res.add(temp);
            up = down;
        }
        return res;
    }
}

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<List<Integer>> levelOrder(TreeNode root) {
        List<List<Integer>> res = new LinkedList<List<Integer>>();
        if (root == null) {
            return res;
        }

        Queue<TreeNode> up = new LinkedList<TreeNode>();
        up.add(root);
        while (!up.isEmpty()) {
            List<Integer> temp = new LinkedList<Integer>();
            int size = up.size();
            while (size > 0) {
                TreeNode cur = up.poll();
                temp.add(cur.val);
                if (cur.left != null) {
                    up.add(cur.left);
                }
                if (cur.right != null) {
                    up.add(cur.right);
                }
                size--;
            }
            res.add(temp);
        }
        return res;
    }
}