Binary-tree-level-order-traversal.cpp

class Solution {
public:
    vector<vector<int>> levelOrder(TreeNode* root) {
        // Create vector of vector for the solution
        vector<vector<int>>solution;
        // If tree is empty: return empty solution; 
        if(root == NULL)
            return solution; 
        // Create queue of TreeNode* and push in the root
        queue<TreeNode*>q; 
        q.push(root); 
        
        // Until the queue is not empty
        while(! q.empty())
        {
            // Create a temporary vector to store the level values
            vector<int>te;
            int size = q.size();
            
            while(size--)
            {
                TreeNode *temp = q.front();
                q.pop(); 
                te.push_back(temp->val);
                // Enqueue temporary children
                if(temp->left != NULL ) q.push(temp->left);
                if(temp->right != NULL) q.push(temp->right);
            }
            // Store the values of the level in the final solution; 
            solution.push_back(te); 
        }
        return solution; 
    }
};