如何在python中返回void

Question

这是著名的硬币找零 dp 问题 - 给定一些硬币返回可能的金额 11=2+2+2+5

arr=[2,5]
def Recur(amount,seq):
    if amount==0:
        print(seq)
        return 
    if amount<0:
        return
    for coin in arr:
        seq+=str(coin)
        Recur(amount-coin,seq)


Recur(11,"")

无论我尝试返回什么，该函数都会返回一个 2，也就是说它在数量达到 0 后继续。我试图返回 0，无，只是返回 - 没有任何效果？它总是在 之后继续

Answer 1

arr=[2,5]
def Recur(amount,seq):
    if amount==0:
        print(seq)
        return 
    if amount<0:
        return
    for coin in arr:
        seq+=str(coin)  # error is in this line since you are 
                        #trying to update seq which persist across the method stack due 
                        #to for loop calls Recur method again with this updated seq 
                        #leading to extra addition of extra coin in seq.
        Recur(amount-coin,seq)


Recur(11,"")

您需要在调用过程中更新 seq 以便进行以下修改：

arr=[2,5]
def Recur(amount,seq):
    if amount==0:
        print(seq)
        return 
    if amount<0:
        return
    for coin in arr:
        Recur(amount-coin,seq+str(coin))


Recur(11,"")