题解 | #从上往下打印二叉树#
从上往下打印二叉树
https://www.nowcoder.com/practice/7fe2212963db4790b57431d9ed259701
很简单的BFS层序遍历，基本操作了。借助队列存储当前层的节点的非空子节点。
class Solution {
public:
vector<int> PrintFromTopToBottom(TreeNode* root) {
if (!root) return {};
queue<TreeNode*> q;
vector<int> res;
q.push(root);
while (!q.empty()) {
auto now = q.front();
q.pop();
res.push_back(now->val);
if (now->left) q.push(now->left);
if (now->right) q.push(now->right);
}
return res;
}
};
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