图解算法

4.1

def s(num):
    if num==[]:
        return 0
    else:
        return num[0]+s(num[1:])
print(s([1,3,2]))

4.2

def s(num):
    if num==[]:
        return 0
    else:
        return 1+s(num[1:])
print(s([1,3,2]))

4.3

def s(num):
    if len(num)==2:
        return num[0] if num[0]>num[1] else num[-1]
    sub_num=s(num[1:])
    return num[0] if num[0]>sub_num else sub_num