HDU 2048 错排

 1 #include <bits/stdc++.h>
 2 
 3 using namespace std;
 4 
 5 double fac[22] = {1,1};
 6 double d[22] = {0,0,1,2};
 7 
 8 int main()
 9 {
10     for(int i=1;i<21;i++)
11         fac[i] = i*fac[i-1];
12 
13     for(int i=4;i<21;i++)
14         d[i] = (i-1)*(d[i-1]+d[i-2]);
15 
16     int c;
17     scanf("%d",&c);
18     while(c--) {
19         int n;
20         scanf("%d",&n);
21         printf("%.2f%c\n",d[n]*100/fac[n],‘%‘);
22     }
23 
24     return 0;
25 }