count_special_integers.py (904B)
| # 2376. Count Special Integers
from math import perm
"""
we call a positive integer special if all of its digits are distinct. given a
positive integer 'n', return the number of special integers that belong to
the interval '[1, n]'
"""
class Solution(object):
def countSpecialNumbers(self, n):
"""
:type n: int
:rtype: int
"""
l = list(map(int, str(n + 1)))
m = len(l)
ans = sum(9 * perm(9, i) for i in range(m - 1))
s = set()
for i, x in enumerate(l):
for y in range(i == 0, x):
if y not in s:
ans += perm(9 - i, m - i - 1)
if x in s:
break
s.add(x)
return ans
if __name__ == "__main__":
obj = Solution()
print(obj.countSpecialNumbers(20))
print(obj.countSpecialNumbers(5))
print(obj.countSpecialNumbers(135))
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