二维前缀和

#include<iostream>
using namespace std;

int a[602][602],s[602][602];
int main(){
    int n,l,r,t;
    cin>>n>>l>>r>>t;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            cin>>a[i][j];
    int count=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            s[i][j]=s[i-1][j] + s[i][j-1] -s[i-1][j-1] +a[i][j];
            //cout<<s[i][j]<<"-";
        }
    }
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++){
            int res=0;
            int x1=i-r,y1=j-r,x2=i+r,y2=j+r;
            if(x1<=1)x1=1;
            if(y1<=1)y1=1;
            if(x2>n)x2=n;
            if(y2>n)y2=n;
            int sum=s[x2][y2]-s[x1-1][y2]-s[x2][y1-1]+s[x1-1][y1-1];
            res=(x2-x1+1)*(y2-y1+1);
            double temp=sum*1.0/res;
           // cout<<i<<" "<<j<<" "<<temp<<endl;
            if(temp<=t)count++;
        }
    cout<<count;
}