Fast Fourier transform (FFT): COGS 2216. Do you think it's KMP?

2216. Do you think it's KMP?

★★★☆ input file: guess.in output file: guess.out Simple comparison
Time limit: 1 s memory limit:

"Title description"

XX is playing two strings of games. First, he took out two strings of S and T,xx want to know how many times T appeared in S and where they were. Note that there may be "?" in T. Character, this character can match any character.

"Input Format"

Two lines of two strings, respectively, representing S and T

"Output Format"

The first line is a positive integer k, which indicates that T appears several times in S.

Next k-line positive integers,

Represents the start position of T each occurrence in S. According to small to large

Sequential output, S subscript starting from 0.

"Sample Input"

Ababcadaca

A?a

"Sample Output"

3

0

5

7

Prompted

For 10% of the data, the length of S and T is not more than 100

For another 20% of the data, there is no "?" in T.

For 100% of the data, s length does not exceed 10^5,t length without exceeding s. S contains only lowercase

Letters, T contains only lowercase letters and "?"

Source

Classic Topics

　　

The problem is the FFT oh, cough ...

1#include <iostream>2#include <cstring>3#include <cstdio>4#include <cmath>5 using namespacestd;6 Const intmaxn=400010;7 Const DoublePi=acos (-1.0);8 CharS[MAXN],T[MAXN];9 intA[MAXN],B[MAXN];Ten structcomplex{ One     Doubler,i; AComplexDoubler_=0.0,Doublei_=0.0){ -R=r_;i=I_; -     } theComplexoperator+(Complex a) { -         returnComplex (r+a.r,i+A.I); -     } -Complexoperator-(Complex a) { +         returnComplex (r-a.r,i-A.I); -     } +Complexoperator*(Complex a) { A         returnComplex (r*a.r-i*a.i,r*a.i+i*A.R); at     } - }; - complex A[MAXN],B[MAXN],C[MAXN],D[MAXN],E[MAXN]; -  - voidRader (Complex *a,intLen) { -     intK; in      for(intI=1,j=len>>1; i<len-1; i++){ -         if(i<j) Swap (A[i],a[j]); toK=len>>1; +          while(j>=k) { -j-=K; thek>>=1; *         } $j+=K;Panax Notoginseng     }         - } the  + voidFFT (Complex *a,intLenintOn ) { A rader (a,len); the      for(intH=2; h<=len;h<<=1){ +Complex WN (cos (-on*pi*2.0/h), sin (-on*pi*2.0/h)); -          for(intj=0; j<len;j+=h) { $Complex W (1,0); $              for(intk=j;k<j+ (h>>1); k++){ -Complex u=A[k]; -Complex v=a[k+ (h>>1)]*W; thea[k]=u+v; -a[k+ (h>>1)]=u-v;Wuyiw=w*WN; the             } -         } Wu     } -     if(on==-1) About          for(intI=0; i<len;i++) $A[i].r/=Len;  - } - intAns[maxn],tot; - intMain () { AFreopen ("guess.in","R", stdin); +Freopen ("Guess.out","W", stdout); thescanf"%s%s", s,t); -     intlens=strlen (s); $     intLent=strlen (t); the      for(intI=0; i<lens;i++) thea[i]=s[i]-'a'+1; the      for(intI=0; i<lent;i++){ the         if(t[i]=='?') -b[lent-i-1]=0; in         Else theb[lent-i-1]=t[i]-'a'+1;  the     } About      the     intlen=1; the      while(len<=lens+lent) len<<=1; the      +      for(intI=0; i<lens;i++) A[i]=complex (1.0,0); -      for(intI=0; i<lent;i++) B[i]=complex (1.0*b[i]*b[i]*b[i],0); theFFT (A,len,1); FFT (B,len,1);Bayi      for(intI=0; i<len;i++) c[i]=a[i]*B[i]; theFFT (c,len,-1);  the      -memset (A,0,sizeof(A)); -memset (B,0,sizeof(B)); the      for(intI=0; i<lens;i++) A[i]=complex (2.0*a[i],0); the      for(intI=0; i<lent;i++) B[i]=complex (1.0*b[i]*b[i],0); theFFT (A,len,1); FFT (B,len,1); the      for(intI=0; i<len;i++) d[i]=a[i]*B[i]; -FFT (d,len,-1); the          thememset (A,0,sizeof(A)); thememset (B,0,sizeof(B));94      for(intI=0; i<lens;i++) A[i]=complex (1.0*a[i]*a[i],0); the      for(intI=0; i<lent;i++) B[i]=complex (1.0*b[i],0); theFFT (A,len,1); FFT (B,len,1); the      for(intI=0; i<len;i++) e[i]=a[i]*B[i];98FFT (e,len,-1); About      -      for(inti=lent-1; i<lens;i++)101         if(Fabs (C[I].R-D[I].R+E[I].R) <1e-5)102ans[++tot]=i-lent+1;103         104printf"%d\n", tot); the      for(intI=1; i<=tot;i++)106printf"%d\n", Ans[i]); 107     return 0;108}

Fast Fourier transform (FFT): COGS 2216. Do you think it's KMP?