void down(int i)
{
int vetsi, j;
while(1){
j = i << 1;
if(j > sn) return;
if(j+1 > sn) vetsi=1;
else vetsi = isGE(j,j+1);
if(vetsi) if isGE(i,j) return; else { swapx(j,i); i=j; }
else if(isGE(i,j+1)) return; else { swapx(j+1,i); i=j+1; }
void fft1x(Complex a[], int n, int iter, int flag)
{
int i, it, j, j1, j2, k, xp, xp2;
double arg, sign, w;
Complex d1, d2, *p, *q, t, ww;
if(n < 2)
{
fprintf(stderr, "Error : n < 2 in fft1()\n");
return;
}
if(iter <= 0)
{
iter = 0;
i = n;
while((i /= 2) != 0) iter++;
}
j = 1;
for(i = 0; i < iter; i++) j *= 2;
if(n != j)
{
fprintf(stderr, "Error : n != 2 ^ k in fft1()\n");
return;
}
sign = (flag == 1)? 1.: -1.;
xp2 = n;
for(it = 0; it < iter; it++)
{
xp = xp2;
xp2 = xp / 2;
w = M_PI / xp2;
for(k = 0; k < xp2; k++)
{
arg = k * w;
ww = tocomplex(cos(arg), sign * sin(arg));
i = k - xp;
for(j = xp, p = a + i + xp, q = a + i + xp + xp2;
j <= n; j += xp, p += xp, q += xp)
{
t = csub(*p, *q);
*p = cadd(*p, *q);
*q = cmul(t, ww);
}
}
}
j1 = n / 2;
j2 = n - 1;
j = 1;
for(i = 1, p = a; i <= j2; i++, p++)
{
if(i < j) swapx(p, a + j - 1);
k = j1;
while(k < j)
{
j -= k;
k /= 2;
}
j += k;
}
if(flag == 0) return;
w = n;
for(i = 0, p = a; i < n; i++, p++) *p = cdiv1(*p, w);
return;
}