POJ 2184(01背包+滚动数组）

01背包 模板题

Program dd;const   maxn=1000;   maxv=100000;   minv=-100000;   NULL=-2139062144;var   n,i,j,ans,p,np:longint;   ts,tf:array[1..maxn] of longint;   f:array[0..1,minv..maxv] of longint;function max(a,b:longint):longint;begin   if a<b then exit(b) else exit(a);end;begin   read(n);   for i:=1 to n do read(ts[i],tf[i]);   fillchar(f,sizeof(f),128);   f[0,0]:=0;   for i:=1 to n do   begin      p:=i mod 2;      fillchar(f[p],sizeof(f[p]),128);      np:=(p+1) mod 2;      for j:=maxv downto minv do      begin         f[p,j]:=f[np,j];         if (minv<=j-ts[i]) and (j-ts[i]<=maxv) then            if (f[np,j-ts[i]]<>NULL) then               f[p,j]:=max(f[p,j],f[np,j-ts[i]]+tf[i]);      end;   end;   ans:=0;   for i:=0 to maxv do      if (f[n mod 2,i]>=0) and (ans<f[n mod 2,i]+i) then ans:=f[n mod 2,i]+i;   writeln(ans);end.