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=150;

inline ll rd(){
    ll x=0;char c=getchar();int neg=1;
    while(c<'0'||c>'9'){if(c=='-') neg=-1;c=getchar();}
    while(c>='0'&&c<='9') x=x*10+c-'0',c=getchar();
    return x*neg;
}

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

int main(){
    int i,j,k;
    d=rd(),N=rd();
    for(i=1;i<=N;i++){
        int a=rd(),b=rd(),c=rd();
        sum[a][b]=c;
    }
    for(i=0;i<=128;i++){
        for(j=0;j<=128;j++){
            sum[i][j]+=(i?sum[i-1][j]:0)+(j?sum[i][j-1]:0)-(i&&j?sum[i-1][j-1]:0);
        }
    }
    ll mm=0;int cnt=0;
    for(i=0;i<=128;i++){
        for(j=0;j<=128;j++){
            int i0=max(0,i-d),j0=max(0,j-d),ii=min(128,i+d),jj=min(128,j+d);
            ll x=sum[ii][jj]-(j0?sum[ii][j0-1]:0)-(i0?sum[i0-1][jj]:0)+(i0&&j0?sum[i0-1][j0-1]:0);
            if(x>mm) mm=x,cnt=1;
            else if(x==mm) cnt++;
        }
    }
    printf("%d %lld
",cnt,mm);
    return 0;
}