BZOJ 3527: [Zjoi2014]力

 1 #include <cmath>
 2 #include <cstdio>
 3 #include <iostream>
 4 
 5 const int siz = 600005;
 6 const double pi = acos(-1);
 7 
 8 inline double sqr(double x) {
 9     return x * x;
10 }
11 
12 int n, rev[siz];
13 double num[siz];
14 
15 struct complex
16 {
17     double r, i;
18 
19     inline complex(double a = 0, double b = 0)
20         : r(a), i(b) {};
21     inline complex operator + (const complex &a) {
22         return complex(r + a.r, i + a.i);
23     }
24     inline complex operator - (const complex &a) {
25         return complex(r - a.r, i - a.i);
26     }
27     inline complex operator * (const complex &a) {
28         return complex(r*a.r - i*a.i, r*a.i + i*a.r);
29     }
30 }a[siz], b[siz];
31 
32 inline void FFT(complex *s, int k)
33 {
34     for (int i = 0; i < n; ++i)
35         if (i < rev[i])
36             std::swap(s[i], s[rev[i]]);
37     
38     for (int h = 2; h <= n; h <<= 1)
39     {
40         complex wn(cos(2*pi*k/h), sin(2*pi*k/h));
41         for (int i = 0; i < n; i += h)
42         {
43             complex w(1, 0);
44             for (int j = 0; j < (h >> 1); ++j, w = w*wn)
45             {
46                 complex t = s[i + j + (h >> 1)]*w;
47                 s[i + j + (h >> 1)] = s[i + j] - t;
48                 s[i + j] = s[i + j] + t;
49             }
50         }
51     }
52     
53     if (k == -1)
54         for (int i = 0; i < n; ++i)
55             s[i].r = s[i].r / n;
56 }
57 
58 signed main(void)
59 {
60     scanf("%d", &n); --n;
61     
62     for (int i = 0; i <= n; ++i)
63         scanf("%lf", &a[i].r);
64         
65     for (int i = 0; i < n; ++i)
66         b[i].r = -1.0 / sqr(n - i);
67         
68     for (int i = n + 1; i <= 2*n; ++i)
69         b[i].r = -1.0 * b[2*n - i].r;
70         
71     int m = n, k = n << 2, len = 0;
72     
73     for (n = 1; n <= k; n <<= 1)++len;
74     
75     for (int i = 0; i < n; ++i)
76         rev[i] = (rev[i >> 1] >> 1) | ((i & 1) << (len - 1));
77         
78     FFT(a, 1);
79     FFT(b, 1);
80     
81     for (int i = 0; i <= n; ++i)
82         a[i] = a[i] * b[i];
83     
84     FFT(a, -1);
85     
86     for (int i = m; i <= 2*m; ++i)
87         printf("%lf\n", a[i].r);
88 }