Leetcode 829. Consecutive Numbers Sum

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.

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x*n+i*(i-1)/2==n, take care the borderline cases:

class Solution:
    def consecutiveNumbersSum(self, N):
        res = 0
        for i in range(1,N+1): #bug1: N+1
            tmp = i*(i-1)//2
            if (N>tmp and (N-tmp)%i == 0): #bug2: N>=tmp
                res += 1
            elif (N<tmp):
                return res
        return res
s = Solution()
print(s.consecutiveNumbersSum(15))