class Solution {
public:
    bool isPossible(vector<int>& nums) {

        unordered_map <int , int > freq , extend;

        for (int i = 0 ; i < nums.size(); i++)
        {
            freq[nums[i]] ++;
        }

        for (int i = 0 ; i < nums.size(); i++)
        {
            int cur = nums[i];
            if (freq[cur] == 0)
                continue;

            if (extend[cur] > 0)
            {
                freq[cur]--;
                extend[cur]--;
                extend[cur + 1]++;
            }
            else if (freq[cur + 1] > 0 && freq[cur + 2] > 0)
            {
                freq[cur]--;
                freq[cur + 1]--;
                freq[cur + 2]--;
                extend[cur + 3]++;
            }
            else
                return false;
        }
        return true;
    }
};