https://leetcode.com/problems/binary-tree-level-order-traversal/
/**
* 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<vector<int>> levelOrder(TreeNode* root) {
vector<vector<int>> rst;
if (!root) {
return rst;
}
queue<TreeNode*> q;
q.push(root);
while(!q.empty()) {
int n = q.size();
vector<int> level;
for (int i = 0; i < n; i++) {
TreeNode* node = q.front();
level.push_back(node->val);
q.pop();
if (node->left) {
q.push(node->left);
}
if (node->right) {
q.push(node->right);
}
}
rst.push_back(level);
}
return rst;
}
};
