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 <vector>
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 cnt = q.size();
			while (cnt > 0) {
				TreeNode *temp = q.front();
				q.pop();
				res.push_back(temp->val);
				if (temp->left) q.push(temp->left);
				if (temp->right) q.push(temp->right);
				cnt--;
			}
		}
		return res;
    }
};