.封装函数，实现如下功能，如：2,5，则求2 + 22 + 222 + 2222 + 22222，可以分别尝试用字符串，列表或者递归实现

# 字符串
def func1(a, b):
    a = str(a)
    sum1 = 0
    for i in range(1, b + 1):
        c = int(a * i)
        sum1 += c
    return sum1


print(func1(2, 5))

# 列表
def func1(a, b):
    a = str(a)
    c_list = []
    for i in range(1, b + 1):
        c = int(a * i)
        c_list.append(c)
    return sum(c_list)


print(func1(2, 5))

# 递归
def func1(x, y):
    sum1 = 0
    for i in range(1, y + 1):
        def f(y):
            if y == 0:
                return 0
            return x * 10 ** (y - 1) + f(y - 1)

        sum1 += f(y)
        y = y - 1
    return sum1


print(func1(2, 5))
# 递归2
def fun2(a, b):
    if b == 1:
        return a
    else:
        return fun2(a, b - 1) + int(‘1‘ * b) * a


print(fun2(2, 2))