# 方法1:
def findMinAndMax(L):    if len(L) == 0:        return None,None    else:        for i in range(len(L)):            return min(L),max(L)
# 方法2:def findMinAndMax(L):    if L==[]:        return None,None    else:        for i in range(len(L)-1):            for j in range(i+1,len(L)):                if L[i]>L[j]:                    L[i],L[j]= L[j],L[i]        return L[0],L[-1]