[剑指offer] 22. 从上往下打印二叉树

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。

---

思路：

队列

class Solution
{
public:
  vector<int> PrintFromTopToBottom(TreeNode *root)
  {
    vector<int> res;
    if (!root)
      return res;
    queue<TreeNode *> que;
    que.push(root);
    while (!que.empty())
    {
      TreeNode *cur = que.front();
      que.pop();
      if(cur)
        res.push_back(cur->val);
      if(cur->left)
        que.push(cur->left);
      if(cur->right)
        que.push(cur->right);
    }
    return res;
  }
};