1996: [Hnoi2010]chorus 合唱队

1996: [Hnoi2010]chorus 合唱队

Time Limit: 4 Sec  Memory Limit: 64 MB
Submit: 1057  Solved: 681
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Description

Input

Output

Sample Input

4
1701 1702 1703 1704

Sample Output

8

HINT

 

Source

 

题解：萌萌哒DP题，其实和我一开始想的暴力方法很接近，基本上就是记忆化暴力，然后转变为循环形式（HansBug：无后效性这玩意就是爽^_^），然后就只管AC啦

（PS：不过话说第一遍的记忆化暴力WA掉了是What Ghost？？？）

/**************************************************************
    Problem: 1996
    User: HansBug
    Language: Pascal
    Result: Accepted
    Time:108 ms
    Memory:8172 kb
****************************************************************/
 
const p=19650827;
var
   i,j,k,l,m,n:longint;
   c:array[0..10000] of longint;
   a:array[0..1005,0..1005,1..2] of longint;
begin
     readln(n);
     for i:=1 to n do
         begin
              read(c[i]);
              a[i,i,0]:=1;
         end;
     readln;
     for i:=n-1 downto 1 do
         for j:=i+1 to n do
             begin
                  a[i,j,0]:=0;a[i,j,1]:=0;
                  if c[i]<c[i+1] then inc(a[i,j,0],a[i+1,j,0]);
                  if c[i]<c[j] then inc(a[i,j,0],a[i+1,j,1]);
                  if c[j]>c[i] then inc(a[i,j,1],a[i,j-1,0]);
                  if c[j]>c[j-1] then inc(a[i,j,1],a[i,j-1,1]);
                  a[i,j,0]:=a[i,j,0] mod p;
                  a[i,j,1]:=a[i,j,1] mod p;
             end;
     writeln((a[1,n,1]+a[1,n,0]) mod p);
     readln;
end.