The kth factor of n

Math Number Theory

70.2% acceptance

Feb 25, 2026

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You are given two positive integers n and k. A factor of an integer n is defined as an integer i where n % i == 0. Consider a list of all factors of n sorted in ascending order, return the kth factor in this list or return -1 if n has less than k factors.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn kth_factor(n: i32, k: i32) -> i32 {
    let mut count = 0i32;
    for i in 1..=n {
      if n % i == 0 {
        count += 1;
        if count == k { return i; }
      }
    }
    -1
  }
}