[BZOJ1996][Hnoi2010]chorus 合唱队 区间dp

1996: [Hnoi2010]chorus 合唱队

Description

1 #include<iostream>
2 #include<cstring>
3 #include<cstdlib>
4 #include<cstdio>
5 #include<cmath>
6 #include<algorithm>
7 #include<queue>
8 #define LL long long
9 #define mod 19650827
10 using namespace std;
11 int read() {
12     char ch=getchar();int x=0,f=1;
13     while(!isdigit(ch)){ch=getchar();}
14     while(isdigit(ch)){x=x*10+ch-'0';ch=getchar();}
15     return x;
16 }
17 int n;
18 int f[1001][1001][2];
19 int a[1001];
20 int main() {
21     scanf("%d",&n);
22     for(int i=1;i<=n;i++) scanf("%d",&a[i]);
23     for(int i=1;i<=n;i++) f[i][i][0]=1;
24     for(int j=1;j<=n;j++) {
25         for(int i=1;i+j<=n;i++) {
26             int k=i+j;
27             if(a[i]<a[k]) f[i][k][0]+=f[i+1][k][1];
28             if(a[i]<a[i+1]) f[i][k][0]+=f[i+1][k][0];
29             if(a[k]>a[i]) f[i][k][1]+=f[i][k-1][0];
30             if(a[k]>a[k-1]) f[i][k][1]+=f[i][k-1][1];
31             f[i][k][1]%=mod;f[i][k][0]%=mod;
32         }
33     }
34     printf("%d",(f[1]
[0]+f[1]
[1])%mod);
35 }