#912. [2018.8雅礼集训8.9]Hunter

https://sjzezoj.com/submission/59289

S2OJ/912/912.cpp

@@ -0,0 +1,45 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+const int mod = 998244353;
+
+int n, w[N], ans = 1;
+
+int binpow(int a, int b, int m) {
+    int res = 1;
+
+    a %= m;
+
+    while (b) {
+        if (b & 1) res = static_cast<long long>(res) * a % m;
+        a = static_cast<long long>(a) * a % m;
+        b >>= 1;
+    }
+
+    return res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> w[i];
+    }
+
+    for (int i = 2; i <= n; i++) {
+        ans = (static_cast<long long>(ans)
+               + static_cast<long long>(w[i]) * binpow(w[i] + w[1], mod - 2, mod) % mod)
+            % mod;
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}