LibreOJ: 3148

「CEOI2016」袋鼠

Author: Macesuted

.vscode/tasks.json

@@ -17,8 +17,8 @@
                 "-Wextra",
                 "-O2",
                 "'-Wl,--stack=512000000'",
-                "-D LOCAL",
-                "-I /Code/libs/ac-library"
+                "-IE:/Code/libs/testlib/",
+                "-DLOCAL",
             ],
             "options": {
                 "cwd": "${fileDirname}"
@@ -78,8 +78,7 @@
                 "-Wextra",
                 "-O2",
                 "'-Wl,--stack=512000000'",
-                "-D LOCAL",
-                "-I E:/Code/libs/ac-library/"
+                "-D LOCAL"
             ],
             "options": {
                 "cwd": "${fileDirname}"

LibreOJ/3148.cpp

@@ -0,0 +1,59 @@
+/**
+ * @file 3148.cpp
+ * @author Macesuted ([email protected])
+ * @date 2022-12-09
+ *
+ * @copyright Copyright (c) 2022
+ *
+ */
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#ifndef LOCAL
+#define endl '\n'
+#endif
+
+bool mem1;
+
+#define maxn 2005
+#define mod 1000000007
+
+int f[maxn][maxn];
+
+int Mod(int a) { return a >= mod ? a - mod : a; }
+int Add(int &a, int b) { return a = Mod(a + b); }
+
+void solve(void) {
+    int n, S, T;
+    cin >> n >> S >> T;
+    f[1][1] = 1;
+    for (int i = 2; i <= n; i++)
+        for (int j = 1; j < i; j++) {
+            int64_t v = f[i - 1][j], cnt = (i > S) + (i > T);
+            if (!v) continue;
+            if (i == S || i == T)
+                Add(f[i][j + 1], v), Add(f[i][j], v);
+            else
+                Add(f[i][j + 1], v * (j + 1 - cnt) % mod), Add(f[i][j - 1], v * (j - 1) % mod);
+        }
+    cout << f[n][1] << endl;
+    return;
+}
+
+bool mem2;
+
+int main() {
+    ios::sync_with_stdio(false), cin.tie(nullptr);
+#ifdef LOCAL
+    cerr << "Memory Cost: " << abs(&mem1 - &mem2) / 1024. / 1024. << "MB" << endl;
+#endif
+
+    int _ = 1;
+    while (_--) solve();
+
+#ifdef LOCAL
+    cerr << "Time Cost: " << clock() * 1000. / CLOCKS_PER_SEC << "MS" << endl;
+#endif
+    return 0;
+}

compile_flags.txt

@@ -1,8 +1,8 @@
 -xc++
+-std=c++20
 -Wall
 -Wextra
 -O2
 -Wl,--stack=512000000
--D LOCAL
--I E:/Code/libs/ac-library/
--std=c++20
+-IE:/Code/libs/testlib/
+-DLOCAL