BZOJ1996: [Hnoi2010]chorus 合唱队 (DP)

就是想水一发

#include <stdio.h>
#include <algorithm>
#include <iostream>
using namespace std;
typedef long long ll;
const ll mod = ;
int q[];
ll dp[][][];

int main()
{
    int n; scanf("%d", &n);
    for(int i = ; i <= n; i++) scanf("%d", &q[i]), dp[i][i][] = ;

    for(int len = ; len <= n; len++)
    {
        for(int i = ; i + len -  <= n; i++)
        {
            int j = i + len - ;
            if(q[j] > q[j - ]) dp[i][j][] = (dp[i][j][] + dp[i][j - ][]) % mod;
            if(q[j] > q[i]) dp[i][j][] = (dp[i][j][] + dp[i][j - ][]) % mod;
            if(q[i] < q[i + ]) dp[i][j][] = (dp[i][j][] + dp[i + ][j][]) % mod;
            if(q[i] < q[j]) dp[i][j][] = (dp[i][j][] + dp[i + ][j][]) % mod;
        }
    }
    printf("%lld\n", (dp[][n][] + dp[][n][]) % mod);
    return ;
}