SRM663 Div1 Easy

ABBADiv1.py

class ABBADiv1:
    def canObtain(self, initial, target):
        def f(initial, rev, target):
            if len(target) == len(initial):
                return initial == target
            
            if initial in target or rev in target:
                if (target[-1] == 'A'):
                    if f(initial, rev, target[:-1]):
                        return True
                if (target[0] == 'B'):
                    t = target[1:]
                    if f(initial, rev, t[::-1]):
                        return True
            return False

        rev = initial[::-1]
        if f(initial, rev, target):
            return "Possible"
        return "Impossible"