1015. Smallest Integer Divisible by K

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

# @lc code=start
using LeetCode

function smallest_repunit_div_by_k(K::Int)
    (K % 2 == 0 || K % 5 == 0) && (return -1)
    r, len = 0, 1
    while true
        r = (10 * r % K + 1) % K
        r == 0 && return len
        len += 1
    end
end
# @lc code=end

smallest_repunit_div_by_k (generic function with 1 method)

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