#631. 故事书（story）

https://sjzezoj.com/submission/71133

S2OJ/631/631.cpp

@@ -0,0 +1,63 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e7 + 5;
+
+int t, p, a, d, n;
+int fac[N], inv[N], fac_inv[N];
+
+constexpr int binpow(int a, int b, int mod) {
+    int res = 1;
+    a %= mod;
+
+    while (b) {
+        if (b & 1) res = static_cast<long long>(res) * a % mod;
+        a = static_cast<long long>(a) * a % mod;
+        b >>= 1;
+    }
+
+    return res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> t >> p;
+
+    fac[0] = 1;
+    for (int i = 1; i < N; i++) {
+        fac[i] = static_cast<long long>(fac[i - 1]) * i % p;
+    }
+
+    inv[0] = inv[1] = 1;
+    for (int i = 2; i < N; i++) {
+        inv[i] = static_cast<long long>(p - (p / i)) * inv[p % i] % p;
+    }
+
+    fac_inv[0] = fac_inv[1] = 1;
+    for (int i = 2; i < N; i++) {
+        fac_inv[i] = static_cast<long long>(fac_inv[i - 1]) * inv[i] % p;
+    }
+
+    while (t--) {
+        cin >> a >> d >> n;
+
+        if (d == 0) {
+            cout << binpow(a, n, p) << endl;
+        } else {
+            int k = static_cast<long long>(a) * inv[d] % p;
+
+            if (k == 0 || n + k - 1 > p) {
+                cout << 0 << endl;
+            } else {
+                cout << static_cast<long long>(fac[n + k - 1]) * fac_inv[k - 1] % p * binpow(d, n, p) % p << endl;
+            }
+        }
+    }
+
+    return 0;
+}