luogu4173 残缺的字符串

there

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
using namespace std;
int n, m, aa[300005], bb[300005], lim=1, tmpcnt, rev[1100005];
const double PI=acos(-1.0);
char ss[300005];
vector<int> vec;
struct Complex{
	double x, y;
	Complex(double xx=0.0, double yy=0.0){
		x = xx;
		y = yy;
	}
	Complex operator+(const Complex &u)const{
		return Complex(x+u.x, y+u.y);
	}
	Complex operator-(const Complex &u)const{
		return Complex(x-u.x, y-u.y);
	}
	Complex operator*(const Complex &u)const{
		return Complex(x*u.x-y*u.y, x*u.y+y*u.x);
	}
	Complex operator*(double u)const{
		return Complex(x*u, y*u);
	}
}a[1100005], b[1100005], c[1100005];
void fft(Complex a[], int opt){
    for(int i=0; i<lim; i++)
        if(i<rev[i])
            swap(a[i], a[rev[i]]);
    for(int i=2; i<=lim; i<<=1){
        int tmp=i>>1;
        Complex wn=Complex(cos(PI*2.0/i), opt*sin(PI*2.0/i));
        for(int j=0; j<lim; j+=i){
            Complex w=Complex(1.0, 0.0);
            for(int k=0; k<tmp; k++){
                Complex tmp1=a[j+k], tmp2=w*a[j+k+tmp];
                a[j+k] = tmp1 + tmp2;
                a[j+k+tmp] = tmp1 - tmp2;
                w = w * wn;
            }
        }
    }
    if(opt==-1)
        for(int i=0; i<lim; i++)
            a[i].x /= lim;
}
int main(){
	cin>>m>>n;
	while(lim<=n+m)	lim <<= 1, tmpcnt++;
	for(int i=0; i<lim; i++)
		rev[i] = (rev[i>>1]>>1) | ((i&1)<<(tmpcnt-1));
	scanf("%s", ss);
	for(int i=0; i<m; i++)
		if(ss[i]!='*')
			aa[i] = ss[i] - 'a' + 1;
	scanf("%s", ss);
	for(int i=0; i<n; i++)
		if(ss[i]!='*')
			bb[i] = ss[i] - 'a' + 1;
	reverse(aa, aa+m);
	for(int i=0; i<m; i++)
		a[i] = Complex(aa[i]*aa[i]*aa[i], 0.0);
	for(int i=0; i<n; i++)
		b[i] = Complex(bb[i], 0.0);
	fft(a, 1);
	fft(b, 1);
	for(int i=0; i<lim; i++)
		c[i] = a[i] * b[i];
	memset(a, 0, sizeof(a));
	memset(b, 0, sizeof(b));
	for(int i=0; i<m; i++)
		a[i] = Complex(aa[i]*aa[i], 0.0);
	for(int i=0; i<n; i++)
		b[i] = Complex(bb[i]*bb[i], 0.0);
	fft(a, 1);
	fft(b, 1);
	for(int i=0; i<lim; i++)
		c[i] = c[i] - a[i] * b[i] * 2.0;
	memset(a, 0, sizeof(a));
	memset(b, 0, sizeof(b));
	for(int i=0; i<m; i++)
		a[i] = Complex(aa[i], 0.0);
	for(int i=0; i<n; i++)
		b[i] = Complex(bb[i]*bb[i]*bb[i], 0.0);
	fft(a, 1);
	fft(b, 1);
	for(int i=0; i<lim; i++)
		c[i] = c[i] + a[i] * b[i];
	fft(c, -1);
	for(int i=m-1; i<n; i++)
		if(fabs(c[i].x)<1e-6)
			vec.push_back(i-m+2);
	cout<<vec.size()<<endl;
	for(int i=0; i<vec.size(); i++)
		printf("%d ", vec[i]);
	printf("\n");
	return 0;
}