打印空心三角形

'''
* 1
* * 2
* * 3
******* 4
'''
a = int(input("输入行数:"))

for i in range(0,a+1):
#空格数
space = a - i
for j in range(space):
print(" ",end="")

#星数
star = 2 * i - 1
for k in range(star):
#z中心判断是否输出为*
if k == 0 or k == star - 1 or i == a:
print("*",end="")
else:
print(" ",end="")


#换行
print()