题解 | #从上往下打印二叉树#

//这道题就是个层序遍历。
#include <queue>
#include <vector>
class Solution {
public:
    vector<int> PrintFromTopToBottom(TreeNode* root) {
		vector<int>result;
		if(root==nullptr)
			return result;
		queue<TreeNode*>q;
		q.push(root);
		while (!q.empty()) {
			TreeNode *top=q.front();
			q.pop();
			result.emplace_back(top->val);
			if (top->left) {
				q.push(top->left);
			}
			if(top->right)
			{
				q.push(top->right);
			}
		}
		return result;
    }
};