面试题32 - I. 从上到下打印二叉树
从上到下打印出二叉树的每个节点,同一层的节点按照从左到右的顺序打印。
例如:
给定二叉树: [3,9,20,null,null,15,7],
3
/
9 20
/
15 7
返回:
[3,9,20,15,7]\
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<int> levelOrder(TreeNode* root) {
queue<TreeNode *> q;
vector<int> result;
if(!root){
return result;
}
q.push(root);
while(!q.empty()){
TreeNode *node = q.front();
result.push_back(node->val);
if(node->left){
q.push(node->left);
}
if(node->right){
q.push(node->right);
}
q.pop();
}
return result;
}
};