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) {
	}
};*/
//其实就是树的层次遍历
#include <queue>
#include <vector>
class Solution {
public:
    vector<int> PrintFromTopToBottom(TreeNode* root) {
			vector<int > tree;
			queue<TreeNode *> qu;

			if (root == nullptr) {
				return tree;
			}

			qu.push(root);

			while (!qu.empty()) {
				TreeNode *node = qu.front();
				qu.pop(); //出队

				tree.push_back(node->val);
				
				if (node->left) qu.push(node->left);
				if (node->right) qu.push(node->right);

			}
			return tree;
    }
};