poj 2140 Herd Sums

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Herd Sums

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 16120		Accepted: 9541

Description

The cows in farmer John‘s herd are numbered and branded with consecutive integers from 1 to N (1 <= N <= 10,000,000). When the cows come to the barn for milking, they always come in sequential order from 1 to N. 

Farmer John, who majored in mathematics in college and loves numbers, often looks for patterns. He has noticed that when he has exactly 15 cows in his herd, there are precisely four ways that the numbers on any set of one or more consecutive cows can add up to 15 (the same as the total number of cows). They are: 15, 7+8, 4+5+6, and 1+2+3+4+5. 

When the number of cows in the herd is 10, the number of ways he can sum consecutive cows and get 10 drops to 2: namely 1+2+3+4 and 10. 

Write a program that will compute the number of ways farmer John can sum the numbers on consecutive cows to equal N. Do not use precomputation to solve this problem. 

Input

* Line 1: A single integer: N 

Output

* Line 1: A single integer that is the number of ways consecutive cow brands can sum to N. 

Sample Input

15

Sample Output

4

題意：求一個數n可以有幾種有連續的數字相加得到

解題思路：i*a+i*(i-1)/2=n，轉換為a=（n-i*(i-1)/2）/i   把i從1到n遍曆一遍，如果（n-i*(i-1)/2）可以整除i那麼i符合

#include <iostream>using namespace std;int main(){int n;while (cin>>n){int count=0;for (int i=1;i<=n;i++){int ans=n-i*(i-1)/2;if (ans<=0)continue;if (ans%i==0){count++;}}cout<<count<<endl;}return 0;}

poj 2140 Herd Sums