Lesson10
Prime and composite numbers
Easy
CountFactors
Count factors of given number n.
Task description
A positive integer D is a factor of a positive integer N if there exists an integer M such that N = D * M.
For example, 6 is a factor of 24, because M = 4 satisfies the above condition (24 = 6 * 4).
Write a function:
class Solution { public int solution(int N); }
that, given a positive integer N, returns the number of its factors.
For example, given N = 24, the function should return 8, because 24 has 8 factors, namely 1, 2, 3, 4, 6, 8, 12, 24. There are no other factors of 24.
Write an efficient algorithm for the following assumptions:
- N is an integer within the range [1..2,147,483,647]. ***
Code Walkthrough
class Solution {
public int solution(int N) {
long i = 1;
int result = 0;
while (i * i < N) {
if (N % i == 0)
result += 2;
i++;
}
if (i * i == N) result += 1;
return result;
}
}
Conclusion
- Detected time complexity: O(sqrt(N))
- Detected space complexity: O(1)