#include<bits/stdc++.h>
using namespace std;
long long n,m,c,a[1010][1010],s[1010][1010];
int main(){
	cin>>n>>m>>c;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			cin>>a[i][j];
			s[i][j]=s[i-1][j]+s[i][j-1]-s[i-1][j-1]+a[i][j];
		}
	}
	long long ma=-1e10,x=0,y=0;
	for(int i=1;i<=n-c+1;i++){
		for(int j=1;j<=n-c+1;j++){
			int x1=i,y1=j,x2=x1+c-1,y2=y1+c-1;
			if(ma<s[x2][y2]-s[x2][y1-1]-s[x1-1][y2]+s[x1-1][y1-1]){
				x=i,y=j;
				ma=s[x2][y2]-s[x2][y1-1]-s[x1-1][y2]+s[x1-1][y1-1];
			}
		}
	}
	cout<<x<<" "<<y;
	return 0;
}

这个是真正的题解：

#include<bits/stdc++.h>
using namespace std;
long long a[1010][1010],s[1010][1010];
int main(){
    long long n,m,c,x,y;
    cin>>n>>m>>c;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            scanf("%lld",&a[i][j]);
            s[i][j]=s[i][j-1]+s[i-1][j]-s[i-1][j-1]+a[i][j];
        }
    }
    long long mx=-1e10;
    for(int x1=1;x1<=n-c+1;x1++){
        for(int y1=1;y1<=m-c+1;y1++){
            int x2=x1+c-1,y2=y1+c-1;
            if(mx<=s[x2][y2]+s[x1-1][y1-1]-s[x2][y1-1]-s[x1-1][y2]){
                mx=s[x2][y2]+s[x1-1][y1-1]-s[x2][y1-1]-s[x1-1][y2];
                x=x1;
                y=y1;
            }
        }
    }
    cout<<x<<" "<<y;
    return 0;
}

我是题解！