[模板]FWT

写起来和fft很像,这里放个板子.

代码:

#include<iostream>
#include<cstdio>
#include<cmath>
#include<ctime>
#include<queue>
#include<map>
#include<algorithm>
#include<cstring>
using namespace std;
#define duke(i,a,n) for(register int i = a;i <= n;i++)
#define lv(i,a,n) for(register int i = a;i >= n;i--)
#define clean(a) memset(a,0,sizeof(a))
const int INF = 1 << 30;
typedef long long ll;
typedef double db;
template <class T>
void read(T &x)
{
    char c;
    bool op = 0;
    while(c = getchar(), c < '0' || c > '9')
        if(c == '-') op = 1;
    x = c - '0';
    while(c = getchar(), c >= '0' && c <= '9')
        x = x * 10 + c - '0';
    if(op) x = -x;
}
template <class T>
void write(T x)
{
    if(x < 0) putchar('-'), x = -x;
    if(x >= 10) write(x / 10);
    putchar('0' + x % 10);
}
#define N 1 << 21 | 3
const int mod = 998244353;
int lim,base;
int a[N],b[N],c[N];
inline int mlt(int x,int y)
{
    return x * 1ll * y % mod;
}
inline int mo(int x,int y)
{
    if(x + y >= mod) return x + y - mod;
    if(x + y < 0) return x + y + mod;
    return x + y;
}
inline int d2(int x)
{
    return (x & 1) ? (x + mod) >> 1 : x >> 1;
}
void fwt(int *a,int d,int op)
{
    for(int i = 1;i < lim;i <<= 1)
    {
        for(int k = 0;k < lim;k += (i << 1))
        {
            for(int l = 0;l < i;l++)
            {
                if(op == 0)
                a[k + l + i] = mo(a[k + l + i],d * a[k + l]);
                else if(op == 1)
                a[k + l] = mo(a[k + l],d * a[k + l + i]);
                else
                {
                    int nx = a[k + l],ny = a[k + l + i];
                    a[k + l] = mo(nx,ny),a[k + l + i] = mo(nx,-ny);
                    if(d == -1)
                    a[k + l] = d2(a[k + l]),a[k + l + i] = d2(a[k + l + i]);
                }
            }
        }
    }
}
int main()
{
    read(base);
    lim = 1 << base;
    duke(i,0,lim - 1) read(a[i]);
    duke(i,0,lim - 1) read(b[i]);
    for(int op = 0;op <= 2;op ++)
    {
        fwt(a,1,op);
        fwt(b,1,op);
        for(int i = 0;i < lim;i++)
        {
            c[i] = mlt(a[i],b[i]);
        }
        fwt(a,-1,op);
        fwt(b,-1,op);
        fwt(c,-1,op);
        duke(i,0,lim - 1)
        {
            printf("%d ",c[i]);
        }
        puts("");
    }
    return 0;
}