[Codeforces Round #164 (Div. 2)]B. Buttons

地址：http://codeforces.com/contest/268/problem/B

找规律，有公式，累加即可

 1 #include <iostream>
 2 #include <algorithm>
 3 using namespace std;
 4 
 5 int n,ans;
 6 
 7 int main()
 8 {
 9     ios::sync_with_stdio(false);
10     int i,j;
11     cin>>n;
12     for(i=n-1,j=1;i>=0 && j<=n;i--,j++)
13     {
14         if(i==0) ans+=j;
15         else
16         {
17             ans+=i*j;
18         }
19     }
20     cout<<ans;
21     return 0;
22 }

 

转载于:https://www.cnblogs.com/tjsuhst/archive/2013/01/29/2881778.html