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 = 19650827;
int q[1005];
ll dp[1005][1005][2];

int main()
{
    int n; scanf("%d", &n);
    for(int i = 1; i <= n; i++) scanf("%d", &q[i]), dp[i][i][0] = 1;

    for(int len = 2; len <= n; len++)
    {
        for(int i = 1; i + len - 1 <= n; i++)
        {
            int j = i + len - 1;
            if(q[j] > q[j - 1]) dp[i][j][1] = (dp[i][j][1] + dp[i][j - 1][1]) % mod;
            if(q[j] > q[i]) dp[i][j][1] = (dp[i][j][1] + dp[i][j - 1][0]) % mod;
            if(q[i] < q[i + 1]) dp[i][j][0] = (dp[i][j][0] + dp[i + 1][j][0]) % mod;
            if(q[i] < q[j]) dp[i][j][0] = (dp[i][j][0] + dp[i + 1][j][1]) % mod;
        }
    }
    printf("%lld\n", (dp[1][n][0] + dp[1][n][1]) % mod);
    return 0;
}