README.md

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

Solutions (Rust)

1. Solution

impl Solution {
    pub fn smallest_repunit_div_by_k(k: i32) -> i32 {
        let mut rem = 0;

        for n in 1..=k {
            rem = (rem * 10 % k + 1 % k) % k;

            if rem == 0 {
                return n;
            }
        }

        -1
    }
}