#2599. 「NOIP2011」计算系数

https://loj.ac/s/1518929

LibreOJ/2599/2599.cpp

@@ -0,0 +1,51 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1005;
+const int mod = 1e4 + 7;
+
+int a, b, k, n, m;
+int fac[N], inv[N];
+
+int binpow(int a, int b) {
+    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;
+}
+
+inline int C(int n, int m) {
+    return static_cast<long long>(fac[n]) * inv[m] % mod * inv[n - m] % mod;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    fac[0] = 1;
+    for (int i = 1; i <= 1000; i++) {
+        fac[i] = static_cast<long long>(fac[i - 1]) * i % mod;
+    }
+
+    inv[0] = inv[1] = 1;
+    for (int i = 2; i <= 1000; i++) {
+        inv[i] = static_cast<long long>(mod - (mod / i)) * inv[mod % i] % mod;
+    }
+
+    for (int i = 2; i <= 1000; i++) {
+        inv[i] = static_cast<long long>(inv[i - 1]) * inv[i] % mod;
+    }
+
+    cin >> a >> b >> k >> n >> m;
+
+    cout << static_cast<long long>(C(k, n)) * binpow(a, n) % mod * binpow(b, m) % mod << endl;
+
+    return 0;
+}