Given a positive integer N, how many ways can we write it as a sum of consecutive positive integers?
Example 1:
Input: 5 Output: 2 Explanation: 5 = 5 = 2 + 3
Example 2:
Input: 9 Output: 3 Explanation: 9 = 9 = 4 + 5 = 2 + 3 + 4
Example 3:
Input: 15 Output: 4 Explanation: 15 = 15 = 8 + 7 = 4 + 5 + 6 = 1 + 2 + 3 + 4 + 5
Note: 1 <= N <= 10 ^ 9.
struct Solution;
impl Solution {
fn consecutive_numbers_sum(n: i32) -> i32 {
let mut i = 2;
let mut res = 1;
while i * i < 2 * n {
if (n - i * (i - 1) / 2) % i == 0 {
res += 1;
}
i += 1;
}
res
}
}
#[test]
fn test() {
let n = 5;
let res = 2;
assert_eq!(Solution::consecutive_numbers_sum(n), res);
let n = 9;
let res = 3;
assert_eq!(Solution::consecutive_numbers_sum(n), res);
let n = 15;
let res = 4;
assert_eq!(Solution::consecutive_numbers_sum(n), res);
let n = 4;
let res = 1;
assert_eq!(Solution::consecutive_numbers_sum(n), res);
}