202104-2 邻域均值

#include <bits/stdc++.h> //100分
using namespace std;
const int maxn = 605;
int n, l, r, t;
int a[maxn][maxn];
int b[maxn][maxn];
int main() // 二维前缀和
{
   cin >> n >> l >> r >> t;
   for (int i = 1; i <= n; i++)
   {
      for (int j = 1; j <= n; j++)
      {
         cin >> a[i][j];
      }
   }
   for (int i = 1; i <= n; i++)
   {
      for (int j = 1; j <= n; j++)
      {
         b[i][j] = b[i - 1][j] + b[i][j - 1] - b[i - 1][j - 1] + a[i][j]; // 预处理
      }
   }
   int ans = 0;
   int sum = 0;
   for (int i = 1; i <= n; i++)
   {
      for (int j = 1; j <= n; j++)
      {
         int x1, x2, y1, y2;
         // 越界
         x1 = max(i - r, 1);
         y1 = max(j - r, 1);
         x2 = min(i + r, n);
         y2 = min(j + r, n);
         sum = b[x2][y2] - b[x1 - 1][y2] - b[x2][y1 - 1] + b[x1 - 1][y1 - 1];
         int num = (x2 - x1 + 1) * (y2 - y1 + 1);
         double w = (double)sum / (double)num;
         if (w <= t)
         {
            ans++;
         }
      }
   }
   cout << ans;
}