bzoj3156

斜率优化dp，比较裸

注意int64的运算

 var f,a,q:array[..] of int64;
     i,n,h,t:longint;
     x,y,z:int64;

 function g(j,k:int64):double;
   var p,q:double;
   begin
     p:=*(f[k]-f[j])+sqr(k)-sqr(j)-k+j;
     q:=*(k-j);
     exit(p/q);
   end;

 begin
   readln(n);
   for i:= to n do
     read(a[i]);
   h:=;
   t:=;
   q[]:=n;
   f[n]:=a[n];
   for i:=n- downto  do
   begin
     while (h<t) and (g(q[h],q[h+])>i) do inc(h);
     x:=q[h];
     y:=i;
     z:=(x-y)*(x-y-);
     f[i]:=(*f[q[h]]+z) div +a[i];
     if i<> then
     begin
       while (h<t) and (g(q[t],i)>g(q[t-],q[t])) do dec(t);
       inc(t);
       q[t]:=i;
     end;
   end;
   writeln(f[]);
 end.