PAT-B 1012. 数字分类(python)

1. py中初始数组，a1=a2=a3=a4=a5=[],  这样a1,a2,a3,a4,a5是指向同一个链表的引用。这和C不一样的。

2. round(number, significant)可以用来四舍五入小数

3. 暂未发现built-in中有average函数，用的是float(sum(a4)) / len(a4)

源码：

if __name__ == "__main__" :
# initialize them seperately
a1=[]
a2=[]
a3=[]
a4=[]
a5=[]

num = raw_input().split(' ')
for i in range(int(num[0])) :
now = int(num[i+1])
if now%10==0 :
a1.append(now)
elif now%5==1 :
a2.append(now)
elif now%5==2 :
a3.append(now)
elif now%5==3 :
a4.append(now)
elif now%5==4 : # cannot use "else" straight, use this contrain
a5.append(now)

if a1==[] :
print "N",
else :
print sum(a1),

if a2==[] :
print "N",
else :
a2_ans=0
for i in range(len(a2)) :
if i%2==0 :
a2_ans = a2_ans + a2[i]
else :
a2_ans = a2_ans - a2[i]
print a2_ans,

if a3==[] :
print "N",
else :
print len(a3),

if a4==[] :
print "N",
else :
print round(float(sum(a4))/len(a4), 1),

if a5==[] :
print "N"
else :
print max(a5)