[BZOJ1218] [HNOI2003]激光炸弹

传送门

http://www.lydsy.com/JudgeOnline/problem.php?id=1218

题目大意

给你n个点的坐标及权值,用r*r的范围最大覆盖是多少

题解

暴力枚举+二维前缀和判断

var sum:array[0..5001,0..5001]of longint; i,j,k:longint; n,r,a,b,mx,my,ans:longint;function max(a,b:longint):longint;begin if a>b then exit(a) else exit(b);end;begin fillchar(sum,sizeof(sum),0); mx:=0; my:=0; readln(n,r); for i:=1 to n do  begin   readln(a,b,sum[a+1,b+1]);   mx:=max(mx,a+1);   my:=max(my,b+1);  end; sum[0,0]:=0; sum[0,1]:=0; sum[1,0]:=0; for i:=1 to max(2*r,mx) do  for j:=1 to my do   inc(sum[i,j],sum[i-1,j]+sum[i,j-1]-sum[i-1,j-1]); ans:=0; for i:=r to max(2*r,mx) do  for j:=r to max(2*r,my) do   ans:=max(ans,sum[i,j]-sum[i-r,j]-sum[i,j-r]+sum[i-r,j-r]); writeln(ans);end.