SRM663 div.1 300 ABBADiv1

ABBADiv1.py

class ABBADiv1:
    def canObtain(self, initial, target):
        def dfs(s):
            if len(s) == len(target):
                return s == target
            if s not in target and s not in rev_target:
                return False
            return dfs(s + 'A') or dfs((s + 'B')[::-1])
        rev_target = target[::-1]
        return "Possible" if dfs(initial) else "Impossible"