题解 | #整数中1出现的次数（从1到n整数中1出现的次数）Python#
整数中1出现的次数（从1到n整数中1出现的次数）
http://www.nowcoder.com/practice/bd7f978302044eee894445e244c7eee6
- 主要找规律，用base*round这个主要规律，base代表该位数的权重，round表示该数前面的值（表示在该位循环了多少次）。用weight表示该数值，former表示该数后面的值（只有当weight为1时有用）。
当weight = 1 时用 base * round+former+1
当weight = 0 时用 base * round
当weight > 1 时用 base * round+base
注意former的计算，用round对base取余计算
weight计算，用round对10取余
round每次要 对10除尽
base每次乘以10
class Solution:
def NumberOf1Between1AndN_Solution(self, n):
num, count, former, weight, base = n, 0, 0, 0, 1
while num != 0:
weight = num % 10
former = n % base
num = num // 10
if weight > 1:
count += num * base + base
elif weight == 1:
count += num * base + former + 1
else:
count += num * base
base = base * 10
return count
s = Solution()
print(s.NumberOf1Between1AndN_Solution(13))
