Binary Tree Level Order Traversal.cpp

/**
 * 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>> ans;
        if(root==NULL)
                return ans;
        queue<TreeNode*> q;
        q.push(root);
        q.push(NULL);
        vector<int> row;
        while(!q.empty())
        {
            TreeNode* temp=q.front();
            q.pop();
            
            if(temp==NULL)
            {
                if(!q.empty())
                    q.push(NULL);
                ans.push_back(row);
                row.clear();
            }
            else
            {
                row.push_back(temp->val);
                if(temp->left!=NULL)
                    q.push(temp->left);
                if(temp->right!=NULL)
                    q.push(temp->right);
            }
            
        }
        return ans;
    }
};