51nod 1285山峰和分段

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 const int N = 5e4+10;
 4 int a[N], n, b[N];
 5 vector<int> vs;
 6 bool ok(int x) {
 7     if(b[n] < x) return false;
 8     int len = n/x;
 9     for(int i = 0; i < x; i ++) {
10         if(b[(i+1)*len]-b[i*len+1] == 0) return false;
11     }
12     return true;
13 }
14 int main() {
15     cin >> n;
16     for(int i = 1; i <= n; i ++) cin >> a[i];
17     for(int i = 2; i < n; i ++) {
18         b[i+1] = (a[i]>a[i-1]&&a[i]>a[i+1]) + b[i];
19     }
20     if(!b[n])return 0*printf("0\n");
21     // for(int i = 1; i<= n; i ++) printf("%d ",b[i] );printf("\n" );
22     for(int i = 2; i <= sqrt(n); i ++) {
23         if(n%i==0) {
24             vs.push_back(i);
25             vs.push_back(n/i);
26         }
27     }
28     sort(vs.begin(),vs.end());
29     for(int i = vs.size()-1; i >= 0; i --) {
30         if(ok(vs[i])) return 0*printf("%d\n",vs[i]);
31     }
32     printf("1\n");
33     return 0;
34 }