题解 | #从上往下打印二叉树#

解法：广搜遍历

/*
struct TreeNode {
	int val;
	struct TreeNode *left;
	struct TreeNode *right;
	TreeNode(int x) :
			val(x), left(NULL), right(NULL) {
	}
};*/
class Solution {
public:
    vector<int> PrintFromTopToBottom(TreeNode* root) {
		vector<int> res;
		if (root == nullptr) return res;
		queue<TreeNode*> q;
		q.push(root);
		while(!q.empty()) {
			int size = q.size();
			for (int i = 0; i < size; ++i) {
				TreeNode* tmp = q.front();
				q.pop();
				res.push_back(tmp->val);
				if (tmp->left) q.push(tmp->left);
				if (tmp->right) q.push(tmp->right);
			}
		}
		return  res;
    }
};