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.
Example 1:
Input: n = 12, k = 3 Output: 3 Explanation: Factors list is [1, 2, 3, 4, 6, 12], the 3rd factor is 3.
Example 2:
Input: n = 7, k = 2 Output: 7 Explanation: Factors list is [1, 7], the 2nd factor is 7.
Example 3:
Input: n = 4, k = 4 Output: -1 Explanation: Factors list is [1, 2, 4], there is only 3 factors. We should return -1.
Example 4:
Input: n = 1, k = 1 Output: 1 Explanation: Factors list is [1], the 1st factor is 1.
Example 5:
Input: n = 1000, k = 3 Output: 4 Explanation: Factors list is [1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, 125, 200, 250, 500, 1000].
Constraints:
1 <= k <= n <= 1000
Solution: Brute Force
Time complexity: O(n)
Space complexity: O(1)
C++
1 2 3 4 5 6 7 8 9 |
// Author: Huahua class Solution { public: int kthFactor(int n, int k) { for (int i = 1; i <= n; ++i) if (n % i == 0 && --k == 0) return i; return -1; } }; |
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