在python中使用递归的青蛙拼图

Question

问题是要编写一个程序来解决青蛙和蟾蜍的难题，这个特定的程序必须使用递归函数，因此它必须没有for/while循环。谜题基本上是左边的青蛙和右边的蟾蜍，这两组被一个空格隔开，获胜的状态是所有蟾蜍都在左边，青蛙在右边，空格再次位于两者之间。程序的预期结果是，用户输入他们想要的青蛙和蟾蜍的数量后，程序将显示拼图的初始状态，然后通过递归打印已解决的拼图，但从已解决状态打印到初始状态，即：

    |Toad|Toad|Frog| |
    |Toad| |Frog|Toad|
    |Toad|Frog| |Toad|
    | |Frog|Toad|Toad|
    |Frog| |Toad|Toad|


def make_state(num_frogs, num_toads):
    state=['Frog']*num_frogs+['']+['Toad']*num_toads
    return state

def find_space(state):
    return state.index('')

def is_frog(state, index):
    if state[index]=='Frog':
        return True
    else:
        return False

def is_toad(state, index):
    if state[index]=='Toad':
        return True
    else:
        return False

def move(state, index):
    newState=list(state)
    newState[newState.index('')]=newState[index]
    newState[index]=''
    return newState

def print_state(state):
    print(*state,sep='|')

def is_win(state):
    if state==state[::-1]:
        return True
    else:
        return False
def solvable(state):
    if is_win(state) == True:
        print(state)
        return True
    elif is_win(state) == False:
        return False
    else:
        N=find_space(state)
        if is_frog(state,N-1):
            newState=move(state,N-1)
            print(newState)
            return solvable(newState)
        
        elif is_frog(state,N-2):
            newState=move(state,N-2)
            print(newState)
            return solvable(newState)
        
        elif is_toad(state,N-1):
            newState=move(state,N-1)
            print(newState)
            return solvable(newState)
        
        elif is_toad(state,N-2):
            newState=move(state,N-2)
            print(newState)
            return solvable(newState)
        else:
            print('False')
     
def main():
    num_frogs=int(input('Enter the number of frogs: \n'))
    num_toads=int(input('Enter the number of toads: \n'))
    print()
    print('Here is the intial state:')
    state=make_state(num_frogs,num_toads)
    print_state(state)
    print()
    print('Here is the solution (in reverse):')
    print(solvable(state))
main()```

I have tried changing the solvable function() to be able to print the expected outcome but the actual outcome that I get is always False.

Answer 1

在比较False、True或None时，应始终使用is

if is_win(state) is True:
    print(state)
    return True
elif is_win(state) is False:
    return False

看看这个试试吧

print( 0 == False ,  0 is False)

但那不是你的问题。。。win返回的是真还是假。。。因此，除了前两个if语句之外，没有其他语句是可访问的（例如，在else中没有任何语句被命中）