题解 | #从上往下打印二叉树#

就是采用了层序遍历

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()){
            TreeNode* node=q.front();
            q.pop();
            res.push_back(node->val);
            if(node->left)    q.push(node->left);
            if(node->right)    q.push(node->right);
        }
        return res;
    }
    
};