Sponsored
Sponsored
This approach involves reversing the stamping process. Instead of trying to form the target from '?' gradually, we attempt to convert the target into '?' by 'un-stamping' in a greedy way.
We can try and 'stamp out' the pattern from the target where it matches. This continues until we've stamped out the entire target or until we determine it's impossible to do so within the given constraints.
Time Complexity: O((N-M+1)*M) where N is the length of target and M is the length of stamp. We effectively iterate through the length of the target and for each possible stamping position, we may iterate through the stamp.
Space Complexity: O(N) to hold the result of the stampping sequence.
The Python implementation uses a list to track the positions that can potentially be converted to '?' by successful stamping. It iterates over possible positions, replaces segments matching the stamp criteria, and then checks if the entire target can become '?'. It appends successfully stamped indices to a list that represents the reverse path of stamping.