Smallest_Integer_Divisible_By_K.py

Given a positive integer K, you need to find the length 
of the smallest positive integer N such that N is divisible by K, 
and N only contains the digit 1.

Return the length of N. If there is no such N, return -1.

Note: N may not fit in a 64-bit signed integer.

Example 1:
Input: K = 1
Output: 1
Explanation: The smallest answer is N = 1, which has length 1.

Example 2:
Input: K = 2
Output: -1
Explanation: There is no such positive integer N divisible by 2.

Example 3:
Input: K = 3
Output: 3
Explanation: The smallest answer is N = 111, which has length 3.
 

Constraints:
1 <= K <= 105

# O(K) Time and O(1) Space
class Solution:
    def smallestRepunitDivByK(self, K: int) -> int:
        
        if K%2 == 0 or K%5 == 0:
            return -1
        
        
        
        N = 0
        
        for i in range(1, K+1):
            
            N = ((N * 10) + 1) % K
            
            if N == 0:
                return i
            
        return -1