[Leetcode] Binary Tree Level Order Traversal II

/**
* 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>> levelOrderBottom(TreeNode* root) {
queue<TreeNode*> S;
vector<vector<int>> reLevel;
int i=0;
int j=0;
if(!root) return reLevel;
S.push(root);
i=1;
TreeNode* p= nullptr;
vector<int> cur;
while(!S.empty()){
if(i == 0){
i=j;
j=0;
reLevel.push_back(cur);
cur.clear();
}
p=S.front();
cur.push_back(p->val);
S.pop();
i=i-1;
if(p->left){
j=j+1;
S.push(p->left);
}
if(p->right){
j=j+1;
S.push(p->right);
}

}
reLevel.push_back(cur);
reverse(reLevel.begin(),reLevel.end());
return reLevel;
}
};