题目: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:层次遍历
/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};*/
class Solution {
public:
vector<int> PrintFromTopToBottom(TreeNode* root) {
if(!root) return {};
vector<int> ans;
deque<TreeNode*> d;
d.push_back(root);
while (!d.empty())
{
TreeNode* t = d.front();
d.pop_front();
ans.push_back(t->val);
if (t->left != nullptr) d.push_back(t->left);
if (t->right != nullptr) d.push_back(t->right);
}
return ans;
}
};