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) {
		queue<TreeNode*> que;
		vector<int> result;
		if (root)
			que.push(root);
		else
		 	return result;
		
		while (!que.empty()){
			int len = que.size();
			while (len--){
				TreeNode* cur = que.front();
				que.pop();
				result.push_back(cur->val);
				if (cur->left)
					que.push(cur->left);
				if (cur->right)
					que.push(cur->right);
			}
		}
		return result;
    }
};