P1719 最大加权矩形

https://www.luogu.com.cn/record/165607779

Luogu/P1719/P1719.cpp

@@ -0,0 +1,46 @@
+#include <iostream>
+#include <limits>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 125;
+
+int n, a[N][N], s[N][N],
+    ans = std::numeric_limits<int>::min();
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) {
+            cin >> a[i][j];
+        }
+    }
+
+    // 二维前缀和
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) {
+            s[i][j] = s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + a[i][j];
+        }
+    }
+
+    // 枚举矩形的左上角和右下角
+    for (int x1 = 1; x1 <= n; x1++) {
+        for (int y1 = 1; y1 <= n; y1++) {
+            for (int x2 = x1; x2 <= n; x2++) {
+                for (int y2 = y1; y2 <= n; y2++) {
+                    ans = std::max(ans, s[x2][y2] - s[x1 - 1][y2] - s[x2][y1 - 1] + s[x1 - 1][y1 - 1]);
+                }
+            }
+        }
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}