luogu2038 [NOIp2014]无线网络发射器选址 (前缀和)

貌似不用做前缀和也能过？

 #include<bits/stdc++.h>
 #define pa pair<int,int>
 #define CLR(a,x) memset(a,x,sizeof(a))
 using namespace std;
 typedef long long ll;
 const int maxn=;

 inline ll rd(){
     ll x=;char c=getchar();int neg=;
     while(c<''||c>''){if(c=='-') neg=-;c=getchar();}
     while(c>=''&&c<='') x=x*+c-'',c=getchar();
     return x*neg;
 }

 int d,N;
 ll sum[maxn][maxn];

 int main(){
     int i,j,k;
     d=rd(),N=rd();
     for(i=;i<=N;i++){
         int a=rd(),b=rd(),c=rd();
         sum[a][b]=c;
     }
     for(i=;i<=;i++){
         for(j=;j<=;j++){
             sum[i][j]+=(i?sum[i-][j]:)+(j?sum[i][j-]:)-(i&&j?sum[i-][j-]:);
         }
     }
     ll mm=;int cnt=;
     for(i=;i<=;i++){
         for(j=;j<=;j++){
             int i0=max(,i-d),j0=max(,j-d),ii=min(,i+d),jj=min(,j+d);
             ll x=sum[ii][jj]-(j0?sum[ii][j0-]:)-(i0?sum[i0-][jj]:)+(i0&&j0?sum[i0-][j0-]:);
             if(x>mm) mm=x,cnt=;
             else if(x==mm) cnt++;
         }
     }
     printf("%d %lld\n",cnt,mm);
     return ;
 }