看球的巴士（vijos1331）

算法：DP

挺简单的，但是一开始却想成了区间DP……

program vijos1331;

const
 maxn=2500;

var
 n,m:longint;
 a:array [0..maxn] of char;
 f:array [0..maxn] of longint;{f[i]表示前i个人最少分多少个巴士。}

procedure init;
var
 i:longint;
begin
 readln(n,m);
 for i:=1 to n do readln(a[i]);
end;

procedure main;
var
 i,j,th,tj:longint;
begin
 fillchar(f,sizeof(f),$2F);
 f[0]:=0;
 f[1]:=1;
 for i:=2 to n do
  begin
   if a[i]='H' then
    begin
     th:=1;
     tj:=0;
    end
   else
    begin
     th:=0;
     tj:=1;
    end;
   for j:=i-1 downto 1 do
    begin
     if a[j]='H' then inc(th) else inc(tj);
     if (abs(th-tj)<=m) or (th=0) or (tj=0) then{如果满足条件的话，这一段就可以再分一组。}
      begin
       if f[j-1]+1<f[i] then
       f[i]:=f[j-1]+1;
      end;
    end;
  end;
end;

begin
 assign(input,'VJ1331.in'); reset(input);
 assign(output,'VJ1331.out'); rewrite(output);

 init;
 main;
 writeln(f[n]);

 close(input); close(output);
end.