BZOJ4259 残缺的字符串

没有传送门 = =

跟上一个题一样 请戳链接

唯一的变化就是柿子稍微一改

\sum f[i]^3 g[j] -2f[i]^2g[j]^2 +f[i]g[j]^3

然后没啥了

注意翻转的位置要改。。。所以不如翻那个不需要改的= =+

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<vector>
#define inf 20021225
#define ll long long
#define db double
#define mxn 1200010
#define eps 1e-8
using namespace std;

const db pi = acos(-1.0);

struct cpx
{
	db x,y;
	cpx(){}
	cpx(db _x,db _y){x=_x,y=_y;}
};

cpx operator +(cpx a,cpx b){return cpx(a.x+b.x,a.y+b.y);}
cpx operator -(cpx a,cpx b){return cpx(a.x-b.x,a.y-b.y);}
cpx operator *(cpx a,cpx b){return cpx(a.x*b.x-a.y*b.y,a.x*b.y+a.y*b.x);}
int rev[mxn];
int init(int n)
{
	int lim=1,l=0;
	while(lim<n) lim<<=1,l++;
	for(int i=1;i<lim;i++)
		rev[i]=(rev[i>>1]>>1)|((i&1)<<(l-1));
	return lim;
}

void fft(cpx *a,int n,int f)
{
	for(int i=1;i<n;i++)	if(rev[i]>i)
		swap(a[rev[i]],a[i]);
	for(int k=2,mid=1;k<=n;k<<=1,mid<<=1)
	{
		cpx Wn = cpx(cos(pi/mid),f*sin(pi/mid));
		for(int i=0;i<n;i+=k)
		{
			cpx w = cpx(1.0,0.0);
			for(int j=0;j<mid;j++,w=w*Wn)
			{
				cpx x=a[i+j],y=w*a[i+mid+j];
				a[i+j] = x+y; a[i+mid+j] = x-y;
			}
		}
	}
	if(f==-1)	for(int i=0;i<n;i++)	a[i].x/=n;
}
char s[mxn],t[mxn]; int ls,lt,ans;
cpx f1[mxn],f2[mxn],f3[mxn],g1[mxn],g2[mxn],g3[mxn],h[mxn];
vector<int> vec;
int id(char ch){return ch=='*'?0:ch-'a'+1;}
int main()
{
	//freopen("1.in","r",stdin);
	scanf("%d%d",&lt,&ls);
	scanf("%s%s",t,s);
	for(int i=0;i<ls;i++)
		f1[i].x=(db)id(s[i]),
		f2[i].x=f1[i].x*f1[i].x,
		f3[i].x=f1[i].x*f2[i].x;
	for(int i=0;i<lt;i++)
		g1[i].x=(db)id(t[lt-i-1]),
		g2[i].x=g1[i].x*g1[i].x,
		g3[i].x=g2[i].x*g1[i].x;	
	//for(int i=0;i<ls;i++)	printf("%lf ",f[i].x);
	int lim=init(ls+lt);
	fft(f1,lim,1); fft(f2,lim,1); fft(f3,lim,1);
	fft(g1,lim,1); fft(g2,lim,1); fft(g3,lim,1);
	for(int i=0;i<lim;i++)	h[i] = f3[i] * g1[i]+ f1[i] * g3[i];
	for(int i=0;i<lim;i++)	h[i] = h[i] - cpx(2.0,0.0)*f2[i]*g2[i];
	fft(h,lim,-1);
	//printf("%lf\n",ful);
	//for(int i=0;i<lim;i++)	printf("%lf ",h[i].x);
	for(int i=0;i<ls-lt+1;i++)
		if(h[i+lt-1].x<0.5)	ans++,vec.push_back(i);
	printf("%d\n",ans);
	for(vector<int>::iterator it=vec.begin();it!=vec.end();it++)
		printf("%d ",(*it)+1);
	return 0;
}
/**
bbabaababaaaaabaaaaaaaabaaabbbabaaabbabaabbbbabbbbbbabbaabbbababababbbbbbaaabaaabbbbbaabbbaabbbbabab
a?aba?abba
*/

 

posted @ 2018-12-26 16:02  寒雨微凝  阅读(59)  评论(0编辑  收藏  举报