[BZOJ1996][Hnoi2010]chorus 合唱队 区间dp

1996: [Hnoi2010]chorus 合唱队

Time Limit: 4 Sec  Memory Limit: 64 MB
Submit: 1853  Solved: 1200
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Description

Input

Output

Sample Input

4
1701 1702 1703 1704

Sample Output

8

HINT

 

Source

简单区间dp

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<queue>
#define LL long long
#define mod 19650827
using namespace std;
int read() {
    char ch=getchar();int x=0,f=1;
    while(!isdigit(ch)){ch=getchar();}
    while(isdigit(ch)){x=x*10+ch-'0';ch=getchar();}
    return x;
}
int n;
int f[1001][1001][2];
int a[1001];
int main() {
    scanf("%d",&n);
    for(int i=1;i<=n;i++) scanf("%d",&a[i]);
    for(int i=1;i<=n;i++) f[i][i][0]=1;
    for(int j=1;j<=n;j++) {
        for(int i=1;i+j<=n;i++) {
            int k=i+j;
            if(a[i]<a[k]) f[i][k][0]+=f[i+1][k][1];
            if(a[i]<a[i+1]) f[i][k][0]+=f[i+1][k][0];
            if(a[k]>a[i]) f[i][k][1]+=f[i][k-1][0];
            if(a[k]>a[k-1]) f[i][k][1]+=f[i][k-1][1];
            f[i][k][1]%=mod;f[i][k][0]%=mod;
        }
    }
    printf("%d",(f[1][n][0]+f[1][n][1])%mod);
}