Containing Duplicated III

class Solution {
    public:
        bool containsNearbyAlmostDuplicate(vector <int> & nums, int k, int t) {
            if(nums.empty() || k==0 || t<0)    return false;
            multiset<long long> kWindow;
            // if lower_bound and upper_bound are not found it returns set.end()

            for (long long i = 0; (i <= k && i<nums.size() ); i++) {
                if (!kWindow.empty()) {
                    long long curr = nums[i];
                    auto it1 = kWindow.upper_bound(curr);
                    auto it2 = kWindow.lower_bound(curr);
                    auto itTemp = prev(it2, 1);

                    // cout << "Set elements: ";
                    // for(auto &x: kWindow)   cout << x << " ";
                    // cout << endl;
                    // cout << "Element coming: " << curr << endl;
                    // cout << "Upper bound: " << *it1 << endl;
                    // cout << "Lower bound: " << *it2 << endl;
                    // //cout << "prevLowerBound: " << *itTemp << endl;
                    // cout << "Upper bound is not present: " << (it1==kWindow.end()) << endl;
                    // cout << "Lower bound is not present: " << (it2==kWindow.end()) << endl;
                    // cout << "Is lower bound the beginning: " << (it2==kWindow.begin()) << endl;
                    // cout << " ============= " << endl;
                    if ( (it2!=kWindow.end() && *it2==curr) || (it2!=kWindow.end() && it2!=kWindow.begin() && curr-*itTemp<=t) || (it1!=kWindow.end() && *it1-curr<=t) || ( abs((long long)(*(kWindow.rbegin())-curr)) <=t) ) {
                        cout <<  abs(*(kWindow.rbegin())-curr) << endl;
                        return true;
                    }
                    kWindow.insert(curr);
                } else {
                    kWindow.insert(nums[i]);
                }
            }

            for (long long i = k+1; i < nums.size(); i++) {
                //oldest element is i-k
                long long toDelete = nums[i - k - 1];
                auto itr = kWindow.find(toDelete);
                kWindow.erase(itr);

                long long curr = nums[i];
                auto it1 = kWindow.upper_bound(curr);
                auto it2 = kWindow.lower_bound(curr);
                auto itTemp = prev(it2, 1);

                //cout << "Set elements: ";
                //for(auto &x: kWindow)   cout << x << " ";
                // cout << endl;
                // cout << "Element coming: " << curr << endl;
                // cout << "Upper bound: " << *it1 << endl;
                // cout << "Lower bound: " << *it2 << endl;
                // //cout << "prevLowerBound: " << *itTemp << endl;
                // cout << "Upper bound is not present: " << (it1==kWindow.end()) << endl;
                // cout << "Lower bound is not present: " << (it2==kWindow.end()) << endl;
                // cout << "Is lower bound the beginning: " << (it2==kWindow.begin()) << endl;
                // cout << " ============= " << endl << endl;

                if ((it2!=kWindow.end() && *it2==curr) || (it2!=kWindow.end() && it2!=kWindow.begin() && curr-*itTemp<=t) || (it1!=kWindow.end() && *it1-curr<=t) || ( abs((long long)(*(kWindow.rbegin())-curr)) <=t) ) {
                    return true;
                }
                kWindow.insert(curr);
            }

            return false;

        }
};