InterviewBit Problems   Stepping Numbers : Unsolved

About the Stepping Numbers : Unsolved category (1)
Wrong result when submitting, right when testing with a custom input (5)
Please add test case A = B = -1 (2)
Upper limit of M (2)
Time complexity of DFS approach (2)
Why we have to do dfs? (1)
Brute force solution is getting accepeted (1)
Memory Limit Exceeded in Python (1)