KK's Point

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)

Total Submission(s): 350 Accepted Submission(s): 121

Problem Description

Our lovely KK has a difficult mathematical problem:He points
N(2≤N≤105)
points on a circle,there are all different.Now he's going to connect the
N
points with each other(There are no three lines in the circle to hand over a point.).KK wants to know how many points are there in the picture(Including the dots of boundary).

Input

The first line of the input file contains an integer
T(1≤T≤10),
which indicates the number of test cases.

For each test case, there are one lines,includes a integer
N(2≤N≤105),indicating
the number of dots of the polygon.

Output

For each test case, there are one lines,includes a integer,indicating the number of the dots.

Sample Input

Sample Output

3

5

Source

BestCoder Round #71 (div.2)

有交点需要有3个或者4个点，三个点的话，交点就是有公共点，相交的更像是一个角，四个点的话就是两天直线相交，因为题中说两两相交，那说明每一条线都会跟其他的线相交，并且不会有重复的交点，显然就是组合数C（4,4）+n，但是数据范围比较大，所以需要unsigned long long

#include<iostream>

#include<cstdio>

#include<cstdlib>

#include<cmath>

using namespace std;

int main()

{

	int t;

	cin>>t;

    while(t--)

    {

		unsigned long long n;

	 	cin>>n;

	  	unsigned long long temp=n*(n-1)*(n-2)/6*(n-3)/4+n;

	    cout<<temp<<endl;

    }

	return 0;

}

巴特西

hdoj--5621--KK's Point（简单数学）

KK's Point

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