Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).
For example:Given binary tree[3,9,20,null,null,15,7],
?? 3
??/ \
?9 ?20
?????/
??? 15? 7
return its level order traversal as:
[ [3], [9,20], [15,7]]
class Solution {
public:
vector<vector<int>> levelOrder(TreeNode* root) {
vector<vector<int>> arr;
if(root==NULL)
return arr;
queue<TreeNode *> q;
q.push(root);
while(!q.empty())
{
int i = 0;
int height = q.size();
vector<int> c;
while(i++<height)
{
TreeNode* t = q.front();
q.pop();
c.push_back(t->val);
if(t->left)
q.push(t->left);
if(t->right)
q.push(t->right);
}
arr.push_back(c);
}
return arr;
}
};
