I've solved almost 650+ problems in codeforce. But i can't solved div-2(A and B) in 1 hour in contest time, sometimes it required 1 hour to solve A.
Now i described how solves 650+ problems. I solved last 200 problem in topicwise like greedy, string, number theory and constructive from 1000-1400 level. But i can't solve as fast in contest time. Now my rating under 1200. Please suggest me in which approach i can solve problem so that i can solve (A and B) in 30 min.