hdu 5328 简单题

 1 #include <algorithm>
 2 #include <iostream>
 3 #include <cstring>
 4 #include <cstdio>
 5 #include <cmath>
 6 using namespace std;
 7 
 8 const int N = 1000000;
 9 const double eps = 1e-8;
10 int a[N];
11 
12 int main ()
13 {
14     int t;
15     scanf("%d", &t);
16     while ( t-- )
17     {
18         int n;
19         scanf("%d", &n);
20         for ( int i = 0; i < n; i++ ) scanf("%d", a + i);
21         if ( n == 1 || n == 2 )
22         {
23             printf("%d\n", n);
24             continue;
25         }
26         int ans = 2, i = 0;
27         while ( i < n - 2 )
28         {
29             int d = a[i] - a[i + 1];
30             int j = i + 1;
31             while ( j < n - 1 && a[j] - a[j + 1] == d )
32             {
33                 j++;
34             }
35             ans = max( ans, j - i + 1 );
36             i = j;
37         }
38         i = 0;
39         while ( i < n - 2 )
40         {
41             double d = a[i] * 1.0 / a[i + 1];
42             int j = i + 1;
43             while ( j < n - 1 && fabs( a[j] * 1.0 / a[j + 1] - d ) < eps )
44             {
45                 j++;
46             }
47             ans = max( ans, j - i + 1 );
48             i = j;
49         }
50         printf("%d\n", ans);
51     }
52     return 0;
53 }