前缀和

前缀和/前缀和.cpp

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+#include <iostream>
+#include <math.h>
+#include <cstring>
+using namespace std;
+int x[3001][3001];
+long long int F[3001][3001];
+long long int line[3001];
+/*
+一维index表示行数，二维index表示列数
+
+
+*/
+int main()
+{
+    int n, m, p;
+    cin >> n >> m >> p;
+    for (int i = 0; i <= n; i++)
+    {
+        for (int j = 0; j <= m; j++)
+        {
+            if (i == 0 || j == 0)
+                x[i][j] = 0;
+            else
+                cin >> x[i][j];
+            if (j == 0 && i == 0)
+                F[i][j] = x[i][j];
+            else if (i == 0)
+                F[i][j] = F[i][j - 1] + x[i][j];
+            else if (j == 0)
+            {
+                line[j] = x[i][j];
+                F[i][j] = F[i - 1][j] + line[j];
+            }
+            else
+            {
+                line[j] = line[j - 1] + x[i][j];
+                F[i][j] = F[i - 1][j] + line[j];
+            }
+        }
+        memset(line, 0, sizeof(line));
+    }
+    // for (int i = 0; i <= n; i++)
+    // {
+    //     for (int j = 0; j <= m; j++)
+    //     {
+    //         cout << F[i][j] << "       ";
+    //     }
+    //     cout << endl;
+    // }
+    long long int max = 0;
+    int r_out = 1, c_out = 1;
+    for (int r = 1; r <= n; r++)
+    {
+        for (int c = 1; c <= m; c++)
+        {
+            int r_up = (r - p - 1 >= 0) ? r - p - 1 : 0;
+            int r_down = (r + p <= n) ? r + p : n - 1;
+            int c_left = (c - p - 1 >= 0) ? c - p - 1 : 0;
+            int c_right = (c + p <= m) ? c + p : m - 1;
+            long long int m = F[r_down][c_right] - F[r_down][c_left] - F[r_up][c_right] + F[r_up][c_left];
+            // cout << r << "  " << c << " " << m << endl;
+            if (m > max)
+            {
+                max = m;
+                r_out = r;
+                c_out = c;
+            }
+        }
+    }
+    cout << max << endl;
+    cout << r_out << " " << c_out;
+    return 0;
+}