UVa 1594 (Floyd判圈) Ducci Sequence

 1 #include <cstdio>
 2 #include <cmath>
 3 
 4 const int maxn = 20;
 5 int n;
 6 int a[maxn], b[maxn], c[maxn];
 7 
 8 void next(int a[])
 9 {
10     for(int i = 0; i < n - 1; i++) a[i] = std::abs(a[i] - a[i + 1]);
11     a[n - 1] = a[0];
12 }
13 
14 bool equal(int a[], int b[])
15 {
16     for(int i = 0; i < n; i++) if(a[i] != b[i]) return false;
17     return true;
18 }
19 
20 int main()
21 {
22     //freopen("in.txt", "r", stdin);
23 
24     int T; scanf("%d", &T);
25     while(T--)
26     {
27         scanf("%d", &n);
28         for(int i = 0; i < n; i++) { scanf("%d", &a[i]); b[i] = a[i]; }
29         a[n] = b[n] = a[0];
30         n++;
31 
32         bool loop = true;
33         for(int i = 0 ; i < 1010; i++)
34         {
35             next(a); next(b); next(b);
36             if(equal(a, c)) { loop = false; break; }
37             if(equal(b, c)) { loop = false; break; }
38             if(equal(a, b)) { loop = true; break; }
39         }
40         printf("%s\n", loop ? "LOOP" : "ZERO");
41     }
42 
43     return 0;
44 }