3209. 花神的数论题

https://hydro.ac/d/bzoj/record/63159b6765233124267c21a2

BZOJ/3209/3209.cpp

@@ -0,0 +1,56 @@
+#include <iostream>
+#include <bitset>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 70;
+const int mod = 1e7 + 7;
+
+long long n, f[N][N][2], ans = 1;
+
+long long binpow(long long a, long long b) {
+    a %= mod;
+
+    long long res = 1;
+
+    while (b) {
+        if (b & 1) res = res * a % mod;
+        a = a * a % mod;
+        b >>= 1;
+    }
+
+    return res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    std::bitset<64> b(n);
+
+    n = 64 - __builtin_clzll(n) - 1 + 1;
+    b <<= 1;
+
+    f[0][0][1] = 1;
+
+    for (int i = 0; i < n; i++) {
+        for (int j = 0; j <= i; j++) {
+            f[i + 1][j][0] += f[i][j][0];
+            f[i + 1][j + 1][0] += f[i][j][0];
+            f[i + 1][j][(b[i + 1] == 0)] += f[i][j][1];
+            if (b[i + 1] == 1) f[i + 1][j + 1][1] += f[i][j][1];
+        }
+    }
+
+    for (int i = 1; i <= 64; i++) {
+        ans = ans * binpow(i, f[n][i][0] + f[n][i][1]) % mod;
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}