binary-tree-level-order-traversal-ii.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> levelOrderBottom(TreeNode* root) {
        queue<TreeNode *> q;
        vector<int> store;
        vector<vector<int>> ans;
        q.push(root);
        if(!root)
            return ans;
        
    //q.push(NULL);

    while (!q.empty())
    {
        
        int sz=q.size();
        while(sz--)
        {
            TreeNode *node = q.front();
            q.pop();
            
            store.push_back(node->val);
            

            if (node->left)
            {
                q.push(node->left);
            }
            if (node->right)
            {
                q.push(node->right);
            }
            //size--;
        }
        //reverse(store.begin(), store.end());
        ans.push_back(store);
        store.clear();
    }

    reverse(ans.begin(), ans.end());
    return ans;

        
    }
};