二维前缀和模板题：P2004 领地选择

思路：就是使用二维前缀和的模板：

先放模板：

#include<iostream>
using namespace std;
#define ll long long
const int maxn = 1e3 + 10;
ll a[maxn][maxn], jx[maxn][maxn];
ll n, m, L, xa, ya, xb, yb;
ll aa, bb, maxx = 0;
int main(){
    cin >> n >> m>>L;
    for (int i = 1; i <= n;++i)
    for (int j = 1; j <= m; ++j)
        cin >> a[i][j];
    
    for (int i = 1; i <= n;++i)
    for (int j = 1; j <= m; ++j)
        jx[i][j] = a[i][j] + jx[i - 1][j] + jx[i][j - 1] - jx[i - 1][j - 1];

    for (int i = 1; i <= n - L+1;++i)
    for (int j = 1; j <= m - L+1; ++j)
    {
        xa = i; ya = j; xb = i + L-1; yb = j + L-1;
        ll sum = jx[xb][yb] - jx[xa-1][yb] - jx[xb][ya-1] + jx[xa-1][ya-1];
        if (maxx < sum){ maxx = sum; aa = xa; bb = ya; }
    }
    cout << aa << " " << bb << endl;
}