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) {
	}
};*///层次遍历
class Solution {
public:
    vector<int> PrintFromTopToBottom(TreeNode* root) {
        vector<int>arr;
        queue<TreeNode*>tree;
        if(!root)return arr;
        tree.push(root);
        while(!tree.empty()){
            TreeNode* temp=tree.front();
            tree.pop();
            arr.push_back(temp->val);
            if(temp->left!=NULL)tree.push(temp->left);
            if(temp->right!=NULL)tree.push(temp->right);
        }
        
        return arr;
    }
};