HDUOJ-Counting Triangles

Counting Triangles

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 1882    Accepted Submission(s): 898

Problem Description

Given an equilateral triangle with n the length of its side, program to count how many triangles in it.

 

 

Input

The length n (n <= 500) of the equilateral triangle's side, one per line.

process to the end of the file

 

 

Output

The number of triangles in the equilateral triangle, one per line.

 

 

Sample Input

1 2 3

 

 

Sample Output

1 5 13

 

 

Author

JIANG, Jiefeng

 

 

Source

http://acm.hdu.edu.cn/showproblem.php?pid=1396

 

Recommend

Ignatius.L

规律在这：

http://mathworld.wolfram.com/TriangleTiling.html

 

代码：

#include<iostream>

#include<cstdio>

using namespace std;

int main()

{

    int n;

    int sum;

    while(cin>>n)

    {

        sum=n*(n+2)*(2*n+1);

        if(n&1)    sum--;

        printf("%d\n",sum/8);

    }

    return 0;

}