剑指32：从上到下打印二叉树

传送门

nowcoder
leetcode

题目描述

从上往下打印出二叉树的每个节点，同层节点从左至右打印。

C++ 代码 - nowcoder

/*
    层次遍历，使用一个队列
*/
class Solution {
public:
    vector<int> PrintFromTopToBottom(TreeNode* root) {
        if (root == nullptr) return vector<int>{};

        vector<int> res;
		queue<TreeNode*> q;
		q.push(root);
		TreeNode* node = nullptr;
		while (!q.empty()) {
			node = q.front(); q.pop();
			res.push_back(node->val);
			if (node->left) q.push(node->left);
			if (node->right) q.push(node->right);
		}
		return res;
    }
};

C++ 代码 - leetcode

/*
    层次遍历
*/
class Solution {
public:
    vector<int> decorateRecord(TreeNode* root) {
        vector<int> res;
        if (!root) return res;

        queue<TreeNode*> q;
        q.push(root);
        while (!q.empty()) {
            TreeNode* node = q.front(); q.pop();
            res.push_back(node->val);
            if (node->left) q.push(node->left);
            if (node->right) q.push(node->right);
        }
        return res;
    }
};