Please give me some hard implementation problems in the rating range of 1800-2100. Thanks

I solved many problems of difficulty 1600-2100. But I am stuck in 1600 rating.What should I do for increase my rating?Please give me suggestions.Thanks

I can't find the time complexity of the following program. Even I can't find a way to calculate its complexity with master theorem. Please help me about how to calculate it. Thanks

My submission : https://codeforces.net/contest/128/submission/114386842

Problem link : https://codeforces.net/contest/128/problem/B