HDU 5328 Problem Killer

Problem Description

   
   
   
   

    
    
    
    You are a "Problem Killer", you want to solve many problems. 
Now you have 
    
    
    
    
    
    
    
     n  problems, the 
    
    
    
    
    
    
    
     i -th problem's difficulty is represented by an integer 
    
    
    
    
    
    
    
     ai  (
    
    
    
    
    
    
    
     1≤ai≤109 ).
For some strange reason, you must choose some integer 
    
    
    
    
    
    
    
     l  and 
    
    
    
    
    
    
    
     r  (
    
    
    
    
    
    
    
     1≤l≤r≤n ), and solve the problems between the 
    
    
    
    
    
    
    
     l -th and the 
    
    
    
    
    
    
    
     r -th, and these problems' difficulties must form an AP (Arithmetic Progression) or a GP (Geometric Progression). 
So how many problems can you solve at most?

You can find the definitions of AP and GP by the following links:
https://en.wikipedia.org/wiki/Arithmetic_progression
https://en.wikipedia.org/wiki/Geometric_progression
   
   
   
   

 

Input

   
   
   
   

    
    
    
    The first line contains a single integer 
    
    
    
    
    
    
    
     T , indicating the number of cases. 
For each test case, the first line contains a single integer 
    
    
    
    
    
    
    
     n , the second line contains 
    
    
    
    
    
    
    
     n  integers 
    
    
    
    
    
    
    
     a1,a2,⋯,an . 


    
    
    
    
    
    
    
     T≤104,∑n≤106 
   
   
   
   

 

Output

   
   
   
   

    
    
    
    For each test case, output one line with a single integer, representing the answer.
   
   
   
   

 

Sample Input

   
   
   
   

    
    
    
    2
5
1 2 3 4 6
10
1 1 1 1 1 1 2 3 4 5
   
   
   
   

 

Sample Output

   
   
   
   

    
    
    
    4
6
   
   
   
   

 

简单题，把差和商处理计算好，求一个最长连续相等的就好了

#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>
#include<queue>
#include<stack>
#include<map>
#include<algorithm>
#include<string>
typedef long long ll;
using namespace std;
const ll maxn=1000005;
int T,n,m;
double a[maxn],b[maxn],c[maxn];

int main()
{
    scanf("%d",&T);
    while (T--)
    {
        scanf("%d",&n);
        for (int i=0;i<n;i++)
        {
            scanf("%lf",&a[i]);
            if (i) 
            {
                b[i]=a[i]-a[i-1];
                if (a[i-1]>1e-7) c[i]=a[i]/a[i-1];
            }
        }
        int l=1,r=1,ans=1;
        for (int i=2;i<n;i++)
        {
            if (b[i]==b[i-1]) l++; else l=1;
            if (c[i]==c[i-1]) r++; else r=1;
            ans=max(ans,max(l,r));
        }
        printf("%d\n",min(ans+1,n));
    }
}

Problem Description

    
    
    
    

     
     
     
     You are a "Problem Killer", you want to solve many problems. 
Now you have 
     
     
     
     
     
     
     
      n  problems, the 
     
     
     
     
     
     
     
      i -th problem's difficulty is represented by an integer 
     
     
     
     
     
     
     
      ai  (
     
     
     
     
     
     
     
      1≤ai≤109 ).
For some strange reason, you must choose some integer 
     
     
     
     
     
     
     
      l  and 
     
     
     
     
     
     
     
      r  (
     
     
     
     
     
     
     
      1≤l≤r≤n ), and solve the problems between the 
     
     
     
     
     
     
     
      l -th and the 
     
     
     
     
     
     
     
      r -th, and these problems' difficulties must form an AP (Arithmetic Progression) or a GP (Geometric Progression). 
So how many problems can you solve at most?

You can find the definitions of AP and GP by the following links:
https://en.wikipedia.org/wiki/Arithmetic_progression
https://en.wikipedia.org/wiki/Geometric_progression
    
    
    
    

 

Input

    
    
    
    

     
     
     
     The first line contains a single integer 
     
     
     
     
     
     
     
      T , indicating the number of cases. 
For each test case, the first line contains a single integer 
     
     
     
     
     
     
     
      n , the second line contains 
     
     
     
     
     
     
     
      n  integers 
     
     
     
     
     
     
     
      a1,a2,⋯,an . 


     
     
     
     
     
     
     
      T≤104,∑n≤106 
    
    
    
    

 

Output

    
    
    
    

     
     
     
     For each test case, output one line with a single integer, representing the answer.
    
    
    
    

 

Sample Input

    
    
    
    

     
     
     
     2
5
1 2 3 4 6
10
1 1 1 1 1 1 2 3 4 5
    
    
    
    

 

Sample Output

    
    
    
    

     
     
     
     4
6