HDU ACM 11 2048 神、上帝以及老天爷

//错排公式  f(n) = (n - 1)(f(n - 1) + f(n - 2)); f(0) = 0, f(1) = 0, f(2) = 1;重要递推

#include <iostream>using namespace std;int main(){int C;int n;cin >> C;while (C--){cin >> n;cout << fixed;cout.precision(2);double Lu[22];Lu[1] = 0;Lu[2] = 1;for (int i = 3; i < n + 1; i++){Lu[i] = (i - 1) * (Lu[i - 1] + Lu[i - 2]);}for (int i = 1; i <= n; i++)Lu[n] /= i;cout << Lu[n] * 100 << "%" << endl;}return 0;}