class Solution {
public:
    vector<vector<int>> divideArray(vector<int>& nums, int k) {
        // sort array from small to large
        // divide into 3 part
        // iterate and check if part[0] - part[2] is bigger than k
        // if yes, return empty vector
        // if no, assign part[0], part[1], part[2] to one vector

        sort(nums.begin(), nums.end());

        vector<vector<int>> ans = {nums.size()/3, vector<int>{}};

        for(int i = 0; i < nums.size(); i+=3){
            if((nums[i+2] - nums[i]) <= k) {
                ans[i/3] = {nums[i], nums[i+1], nums[i+2]};
            } else {
                return vector<vector<int>>{};
            }
        }

        return ans;
    }
};