多校联赛第三场

Permutation Bo

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 0    Accepted Submission(s): 0
Special Judge

Problem Description

There are two sequences  h1∼hn and  c1∼cn.  h1∼hn is a permutation of  1∼n. particularly,  h0=hn+1=0.

We define the expression  [condition] is 1 when  condition is True,is 0 when  condition is False.

Define the function  f(h)=∑ni=1ci[hi>hi−1  and  hi>hi+1]

Bo have gotten the value of  c1∼cn, and he wants to know the expected value of  f(h).

 

Input

This problem has multi test cases(no more than  12).

For each test case, the first line contains a non-negative integer  n(1≤n≤1000), second line contains  n non-negative integer  ci(0≤ci≤1000).

 

Output

For each test cases print a decimal - the expectation of  f(h).

If the absolute error between your answer and the standard answer is no more than  10−4, your solution will be accepted.

 

Sample Input

4 3 2 4 5 5 3 5 99 32 12

 

Sample Output

6.000000 52.833333

 

找规律！！

#include
#include
#include
#include

using namespace std;
int n;
int c[1005];


double sum,aver,sum1;

int main()
{ 
	int i,j,k;

	while(scanf("%d",&n)!=EOF)
	{

		memset(c,0,sizeof(c));
		sum1=0;

		for(i=1;i<=n;i++)
		{
			scanf("%d",&c[i]);
			if(i!=1&&i!=n)
				sum1+=c[i];
		}
		
		
		if(n==1)  {
			aver=c[1];
			printf("%lf\n",aver);
		}
		else
		{
			aver=(sum1/3*2+c[1]+c[n])/2;
			printf("%lf\n",aver);		
		}
	}
	return 0;
} 

Teacher Bo

Time Limit: 4000/2000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 0    Accepted Submission(s): 0

Problem Description

Teacher BoBo is a geography teacher in the school.One day in his class,he marked  N points in the map,the  i-th point is at  (Xi,Yi).He wonders,whether there is a tetrad  (A,B,C,D)(A<B,C<D,A≠CorB≠D) such that the manhattan distance between A and B is equal to the manhattan distance between C and D.

If there exists such tetrad,print "YES",else print "NO".

 

Input

First line, an integer  T. There are  T test cases. (T≤50)

In each test case,the first line contains two intergers, N, M, means the number of points and the range of the coordinates. (N,M≤105).

Next N lines, the  i-th line shows the coordinate of the  i-th point. (Xi,Yi)(0≤Xi,Yi≤M).

 

Output

T lines, each line is "YES" or "NO".

 

Sample Input

2 3 10 1 1 2 2 3 3 4 10 8 8 2 3 3 3 4 4

 

Sample Output

YES NO

map实现！

#include
#include