练一下斜率优化
1 var s1,s2,f:array[0..1000010] of int64; 2 q,a,b:array[0..1000010] of longint; 3 i,n,h,t,j:longint; 4 5 function g(j,k:longint):double; 6 var a,b:double; 7 begin 8 a:=f[j]-f[k]-s2[j]+s2[k]; 9 b:=s1[k]-s1[j]; 10 exit(a/b); 11 end; 12 13 begin 14 readln(n); 15 for i:=1 to n do 16 read(a[i]); 17 for i:=1 to n do 18 begin 19 read(b[i]); 20 s1[i]:=s1[i-1]+b[i]; 21 s2[i]:=s2[i-1]+int64(b[i])*int64(n-i+1); 22 end; 23 h:=0; 24 t:=0; 25 for i:=1 to n do 26 begin 27 while (h<t) and (g(q[h],q[h+1])>=n-i+1) do inc(h); 28 j:=q[h]; 29 f[i]:=f[j]+a[i]+s2[i-1]-s2[j]-(s1[i-1]-s1[j])*int64(n-i+1); 30 while (h<t) and (g(q[t],i)>=g(q[t-1],q[t])) do dec(t); 31 inc(t); 32 q[t]:=i; 33 end; 34 writeln(f[n]); 35 end.
