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#

• 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))