剑指offer：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。

/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};*/
class Solution {
public:
//采用层序遍历
vector<int> PrintFromTopToBottom(TreeNode* root) {
vector<int> output;
queue<TreeNode *> q;
if(root == NULL)
return output;

q.push(root);
while(!q.empty())
{
TreeNode *node = q.front();
q.pop();
output.push_back(node->val);

if(node->left != NULL)
q.push(node->left) ;
if(node->right != NULL)
q.push(node->right);
}
return output;
}
};