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 + ;

ll a[maxn][maxn], jx[maxn][maxn];

ll n, m, L, xa, ya, xb, yb;

ll aa, bb, maxx = ;

int main(){

    cin >> n >> m>>L;

    for (int i = ; i <= n;++i)

    for (int j = ; j <= m; ++j)

        cin >> a[i][j];

    for (int i = ; i <= n;++i)

    for (int j = ; j <= m; ++j)

        jx[i][j] = a[i][j] + jx[i - ][j] + jx[i][j - ] - jx[i - ][j - ];

    for (int i = ; i <= n - L+;++i)

    for (int j = ; j <= m - L+; ++j)

    {

        xa = i; ya = j; xb = i + L-; yb = j + L-;

        ll sum = jx[xb][yb] - jx[xa-][yb] - jx[xb][ya-] + jx[xa-][ya-];

        if (maxx < sum){ maxx = sum; aa = xa; bb = ya; }

    }

    cout << aa << " " << bb << endl;

}