UVa 10534 DP LIS Wavio Sequence

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <algorithm>
 5 using namespace std;
 6 
 7 const int maxn = 10000 + 10;
 8 
 9 int n;
10 
11 int a[maxn], l[maxn], r[maxn];
12 int g[maxn];
13 
14 void LIS(int d[])
15 {
16     memset(g, 0x3f, sizeof(g));
17     for(int i = 0; i < n; i++)
18     {
19         int k = lower_bound(g+1, g+1+n, a[i]) - g;
20         d[i] = k;
21         g[k] = a[i];
22     }
23 }
24 
25 int main()
26 {
27     while(scanf("%d", &n) == 1)
28     {
29         for(int i = 0; i < n; i++) scanf("%d", a + i);
30         LIS(l);
31         reverse(a, a + n);
32         LIS(r);
33 
34         int ans = 1;
35         for(int i = 0; i < n; i++) ans = max(ans, min(l[i], r[n-1-i]));
36         printf("%d\n", ans * 2 - 1);
37     }
38 
39     return 0;
40 }