leetcode-problems/107.cpp at main · nikhilsahu-0/leetcode-problems · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
/**
 * 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) {
        if(root == NULL)return {};

            queue<TreeNode*> q;
            q.push(root);
            q.push(NULL);
            vector<int> v;
            vector<vector<int>> vi;
            while(!q.empty()){
                TreeNode *temp = q.front();
                q.pop();
                if(temp != NULL){
                    v.push_back(temp->val);
                    if(temp->left != NULL)q.push(temp->left);
                    if(temp->right != NULL)q.push(temp->right);
                }else {
                    vi.push_back(v);
                    v = {};
                    if(q.empty())break;
                    else q.push(NULL);
                }
            }
        reverse(vi.begin(),vi.end());
        return vi;
    }
};