LeetCode "Contains Duplicate III"

Lesson learnt: std::multiset<T> is a heap structure supporting random removal...

class Solution 
{    
public:
    
    bool containsNearbyAlmostDuplicate(vector<int>& nums, int k, int t) 
    {
        if (t < 0) return false;
        size_t len = nums.size();
        
        k = std::min(k, (int)len - 1);
        if (k <= 0) return false;

        std::multiset<long long> hp;
        for (int i = 0; i < len; i ++)
        {
            if (i > k)
            {
                hp.erase(nums[i - k - 1]);    // heap maintain
            }
            
            int curr = nums[i];
            if (hp.find(curr) != hp.end())
                return true;

            //    Upper bound
            auto up = hp.upper_bound(curr);
            if(up != hp.end() && *up - curr <= t)
                return true;

            //    Lower bound
            if (up != hp.begin())
            {
                --up;
                if ((curr - *up) <= t)
                    return true;
            }

            hp.insert(curr);
        }

        return false;
    }
};

 Or, another incredibly smart solution: bucketing! https://leetcode.com/discuss/38206/ac-o-n-solution-in-java-using-buckets-with-explanation

class Solution 
{    
public:
    
    bool containsNearbyAlmostDuplicate(vector<int>& nums, int k, int t) 
    {
        if (k < 1 || t < 0) return false;
        
        unordered_map<long long, long long> hm;
        for (int i = 0; i < nums.size(); i ++)
        {
            long long nv = (long long)nums[i] - INT_MIN;
            long long bucket = nv / ((long long)t + 1);
            if ( hm.find(bucket) != hm.end() || 
                 (hm.find(bucket + 1) != hm.end() && (hm[bucket + 1] - nv) <= t) ||
                 (hm.find(bucket - 1) != hm.end() && (nv - hm[bucket - 1]) <= t)
                 )
                 return true;
            //    
            if (hm.size() >= k)
            {
                long long lastBucket = ((long long)nums[i - k] - INT_MIN) / ((long long)t + 1);
                hm.erase(lastBucket);
            }
            hm[bucket] = nv;
        }

        return false;
    }
};