题解:
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]
提示:
节点总数 <= 1000
题解:
层序遍历:
/**
* 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) {
vector<int>ans;
if(!root) return ans;
queue<TreeNode* >q;
q.push(root);
while(!q.empty())
{
int len = q.size();
for(int i = 0;i<len;i++)
{
TreeNode* t = q.front();
q.pop();
ans.push_back(t->val);
if(t->left)
q.push(t->left);
if(t->right)
q.push(t->right);
}
}
return ans;
}
};