空心三角形练习
#崔鑫阳 2019.2.24
star_num=int(input("请输入星星的层数"))
for i in range(star_num):
for t in range(i+star_num):
if t==star_num-i-1 or t==star_num+i-1 or i==star_num-1:
print("*",end='')
else:
print(' ',end='')
print()