UVa10570 Meeting with Aliens (枚举)

 1 #include <cstdio>
 2 #include <algorithm>
 3 #include <cstring>
 4 using namespace std;
 5 
 6 const int maxn = 500 + 5;
 7 
 8 int n, data[maxn], idex[maxn], a[maxn], aIdex[maxn];
 9 
10 int main() {
11     while (scanf("%d", &n) == 1 && n) {
12         for (int i = 0; i < n; i++) {
13             scanf("%d", &data[i]); --data[i];
14             idex[data[i]] = i;
15         }
16         int ans = maxn;
17         for (int start = 0; start < n; start++) {
18             memcpy(a, data, sizeof(data));
19             memcpy(aIdex, idex, sizeof(idex));
20             int cnt1 = 0;
21             for (int i = 0; i < n; i++)
22                 if (a[i] != (start + i) % n) {
23                     swap(a[i], a[aIdex[(start + i) % n]]);
24                     swap(aIdex[a[aIdex[(start + i) % n]]], aIdex[(start + i) % n]);
25                     cnt1++;
26                 }
27             memcpy(a, data, sizeof(data));
28             memcpy(aIdex, idex, sizeof(idex));
29             int cnt2 = 0;
30             for (int i = 0; i < n; i++)
31                 if (a[i] != (start - i + n) % n) {
32                     swap(a[i], a[aIdex[(start - i + n) % n]]);
33                     swap(aIdex[a[aIdex[(start - i + n) % n]]], aIdex[(start - i + n) % n]);
34                     cnt2++;
35                 }
36             ans = min(ans, min(cnt1, cnt2));
37         }
38         printf("%d\n", ans);
39     }
40     return 0;
41 }