#13368. 「NOIP2022模拟赛pb」丝线

http://www.nfls.com.cn:10611/submission/244428

NFLSOJ/13368/13368.cpp

@@ -0,0 +1,38 @@
+#include <iostream>
+#include <fstream>
+
+// using std::cin;
+// using std::cout;
+std::ifstream cin("string.in");
+std::ofstream cout("string.out");
+const char endl = '\n';
+
+const int N = 1e6 + 5;
+const int mod = 998244353;
+
+int a, b, inv[N << 2], ans;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> a >> b;
+
+    inv[0] = inv[1] = 1;
+
+    for (int i = 2; i <= a + a + b; i++) {
+        inv[i] = static_cast<long long>(mod - mod / i) * inv[mod % i] % mod;
+    }
+
+    for (int i = 1; i <= a; i++) {
+        ans = (static_cast<long long>(ans) + inv[2 * i - 1]) % mod;
+    }
+
+    for (int i = 1; i <= b; i++) {
+        ans = (static_cast<long long>(ans) + inv[2 * a + i]) % mod;
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}