Program to count n digit integers where digits are strictly increasing in Python

PythonServer Side ProgrammingProgramming

Suppose we have a number n, we have to find the number of n-digit positive integers such that the digits are in strictly increasing order.

So, if the input is like n = 3, then the output will be 84, as numbers are 123, 124, 125, ..., 678,789

To solve this, we will follow these steps −

  • if n < 9 is non-zero, then

    • return Combination (9Cn)

  • otherwise,

    • return 0

Let us see the following implementation to get better understanding −

Example

 Live Demo

from math import factorial as f
class Solution:
   def solve(self, n):
      if n < 9:
         return f(9) / f(n) / f(9 - n)
      else:
         return 0

ob = Solution()
print(ob.solve(3))

Input

3

Output

84
raja
Published on 09-Oct-2020 13:44:09
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