1996: [Hnoi2010]chorus 合唱队 - BZOJ

Description

Input
Output

Sample Input
4
1701 1702 1703 1704
Sample Output
8
HINT

 

水题，区间dp，f[l,r,k]表示区间[l,r]最后一个是左（k=0）还是右（k=1）的方案数

 1 const
 2         maxn=1010;
 3         h=19650827;
 4 var
 5         f:array[0..maxn,0..maxn,0..1]of longint;
 6         a:array[0..maxn]of longint;
 7         n:longint;
 8  
 9 procedure init;
10 var
11         i:longint;
12 begin
13         read(n);
14         for i:=1 to n do
15           begin
16             read(a[i]);
17             f[i,i,0]:=1;
18           end;
19 end;
20  
21 procedure dp;
22 var
23         i,j:longint;
24 begin
25         for i:=1 to n-1 do
26           for j:=1 to n-i do
27             begin
28               f[j,j+i,0]:=(longint(a[j]<a[j+1])*f[j+1,j+i,0]+longint(a[j]<a[j+i])*f[j+1,j+i,1])mod h;
29               f[j,j+i,1]:=(longint(a[j+i]>a[j])*f[j,j+i-1,0]+longint(a[j+i]>a[j+i-1])*f[j,j+i-1,1])mod h;
30             end;
31         writeln((f[1,n,0]+f[1,n,1])mod h);
32 end;
33  
34 begin
35         init;
36         dp;
37 end.
View Code

 

posted @ 2014-04-24 21:05  Randolph87  阅读(174)  评论(0)  编辑  收藏  举报