AC

#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>

using namespace std;

struct TreeNode {

int val;
TreeNode* left;
TreeNode* right;
TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}

};

TreeNode* buildTree(vector& nodes, int& index) {

if (index >= nodes.size() || nodes[index] == -1) {
    index++;
    return nullptr;
}
TreeNode* root = new TreeNode(nodes[index]);
index++;
root->left = buildTree(nodes, index);
root->right = buildTree(nodes, index);
return root;

}

vector<vector> levelOrderBottom(TreeNode* root) {

vector<vector<int>> result;
if (!root) return result;
queue<TreeNode*> q;
q.push(root);
while (!q.empty()) {
    int levelSize = q.size();
    vector<int> currentLevel;
    for (int i = 0; i < levelSize; ++i) {
        TreeNode* node = q.front();
        q.pop();
        currentLevel.push_back(node->val);
        if (node->left) q.push(node->left);
        if (node->right) q.push(node->right);
    }
    result.push_back(currentLevel);
}
reverse(result.begin(), result.end());
return result;

}

int main() {

vector<int> nodes;
int num;
while (cin >> num) {
    nodes.push_back(num);
}
int index = 0;
TreeNode* root = buildTree(nodes, index);
vector<vector<int>> levels = levelOrderBottom(root);
for (const auto& level : levels) {
    for (size_t i = 0; i < level.size(); ++i) {
        if (i != 0) cout << " ";
        cout << level[i];
    }
    cout << endl;
}
return 0;

}