【剑指offer】从上往下打印二叉树（树）

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题目描述

从上往下打印出二叉树的每个节点，同层节点从左至右打印。

链接

https://www.nowcoder.com/practice/7fe2212963db4790b57431d9ed259701?tpId=13&tqId=11175&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking

代码

/*
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> ans;
		queue<TreeNode*> q;
		if(root == NULL){
			return ans;
		}
		else{
			q.push(root);
		}
		while(!q.empty()){
			TreeNode* temp = q.front();
			ans.push_back(temp->val);
			if(temp->left){
				q.push(temp->left);
			}
			if(temp->right){
				q.push(temp->right);
			}
			q.pop();
		}
		return ans;
    }
};