题解 | #从上往下打印二叉树#

/*
struct TreeNode {
	int val;
	struct TreeNode *left;
	struct TreeNode *right;
	TreeNode(int x) :
			val(x), left(NULL), right(NULL) {
	}
};*/
#include <queue>
class Solution {
public:
	vector<int>res;
    vector<int> PrintFromTopToBottom(TreeNode* root) {
		queue<TreeNode*>que;
		if(root == nullptr)
		{
			return res;
		}
		que.push(root);	//像队列中插入元素
		while(!que.empty())
		{
			TreeNode* temp = que.front();
			if(temp->left != nullptr)
			{
				que.push(temp->left);
			}
			if(temp->right != nullptr)
			{
				que.push(temp->right);
			}

			res.push_back(temp->val);
			que.pop();
		}
		return res;
    }
};