'commit'

TangDou/Topic/PrefixAndSuffix/P2004.cpp

@@ -0,0 +1,27 @@
+#include <bits/stdc++.h>
+using namespace std;
+const int N = 1010;
+int n, m, c;
+int a[N][N], s[N][N];
+int mx = INT_MIN;
+
+int main() {
+    cin >> n >> m >> c;
+    for (int i = 1; i <= n; i++)
+        for (int j = 1; j <= m; j++) {
+            cin >> a[i][j];
+            s[i][j] = s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + a[i][j]; // 构建二维前缀和
+        }
+
+    int x, y;
+    for (int i = c; i <= n; i++) // 边长为c
+        for (int j = c; j <= m; j++) {
+            if (s[i][j] - s[i - c][j] - s[i][j - c] + s[i - c][j - c] > mx) {
+                mx = s[i][j] + s[i - c][j - c] - s[i - c][j] - s[i][j - c];
+                x = i - c + 1;
+                y = j - c + 1;
+            }
+        }
+    printf("%d %d", x, y);
+    return 0;
+}

TangDou/Topic/【前缀和与差分】题单.md

@@ -421,7 +421,37 @@ int main() {
 ```
 
 #### [$P2004$ 领地选择](https://www.luogu.com.cn/problem/P2004)
+二维前缀和祼题，不解释。
 
+```cpp {.line-numbers}
+#include <bits/stdc++.h>
+using namespace std;
+const int N = 1010;
+int n, m, c;
+int a[N][N], s[N][N];
+int mx = INT_MIN;
+
+int main() {
+    cin >> n >> m >> c;
+    for (int i = 1; i <= n; i++)
+        for (int j = 1; j <= m; j++) {
+            cin >> a[i][j];
+            s[i][j] = s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + a[i][j]; // 构建二维前缀和
+        }
+
+    int x, y;
+    for (int i = c; i <= n; i++) // 边长为c
+        for (int j = c; j <= m; j++) {
+            if (s[i][j] - s[i - c][j] - s[i][j - c] + s[i - c][j - c] > mx) {
+                mx = s[i][j] + s[i - c][j - c] - s[i - c][j] - s[i][j - c];
+                x = i - c + 1;
+                y = j - c + 1;
+            }
+        }
+    printf("%d %d", x, y);
+    return 0;
+}
+```
 #### [$P3397$ 地毯](https://www.luogu.com.cn/problem/P3397)
 
 **分析**