hdu 5400 Arithmetic Sequence（模拟）

Problem Description

A sequence b1,b2,⋯,bn are called (d1,d2)-arithmetic sequence if and only if there exist i(≤i≤n) such that for every j(≤j<i),bj+=bj+d1 and for every j(i≤j<n),bj+=bj+d2.

Teacher Mai has a sequence a1,a2,⋯,an. He wants to know how many intervals [l,r](≤l≤r≤n) there are that al,al+,⋯,ar are (d1,d2)-arithmetic sequence.
 

Input

There are multiple test cases.

For each test case, the first line contains three numbers n,d1,d2(≤n≤,|d1|,|d2|≤), the next line contains n integers a1,a2,⋯,an(|ai|≤).
 

Output

For each test case, print the answer.

 

Sample Input

  - 
   -  

 

Sample Output

 

Author

xudyh

 

Source

2015 Multi-University Training Contest 9

 

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 using namespace std;
 #define N 100006
 #define ll long long
 int n,k1,k2;
 int a[N];
 int dp[N];
 int main()
 {
     while(scanf("%d%d%d",&n,&k1,&k2)==)
     {
         for(int i=;i<=n;i++)
         {
             scanf("%d",&a[i]);
         }

         memset(dp,,sizeof(dp));
         for(int i=;i<n;i++)
         {
             if(a[i+]==a[i]+k1)
                dp[i+]=;
             else if(a[i+]==a[i]+k2)
                 dp[i+]=;
             else dp[i+]=;
         }

         ll ans=;
         ll tmp=;
         for(int i=;i<=n;i++)
         {
             if(dp[i]==)
             {
                 if(dp[i-]==)
                 {
                     tmp=;
                 }
                 else
                     tmp++;
                 ans=ans+tmp+;
             }
             else if(dp[i]==)
             {
                 tmp++;
                 ans=ans+tmp+;
             }
             else
             {
                 ans++;
                 tmp=;
             }

         }
         printf("%I64d\n",ans);
     }
     return ;
 }