poj3461 KMP模板 或 哈希

kmp模板题，也可用哈希

kmp版

#include<iostream>#include<cstdio>#include<cstring>#include<string>#include<cstdlib>#include<cmath>#include<ctime>#include<algorithm>#include<iomanip>#include<cctype>#include<queue>using namespace std;const int N=1e6+5;char s[N],t[N];int sn,tn,bz=1,next[N];void getnext(){    for(int i=1,j=0;i<tn;i++)    {        while(j&&t[i]!=t[j])j=next[j-1];        if(t[i]==t[j])j++;        next[i]=j;    }}void kmp(){    for(int i=0,j=0;i<sn;i++)    {        while(j&&s[i]!=t[j])j=next[j-1];        if(s[i]==t[j])j++;        if(j==tn)        {            bz=0;            cout<<i-tn+2<<'\n';        }    }}int main(){    //freopen("lx.in","r",stdin);    scanf("%s%s",s,t);    sn=strlen(s),tn=strlen(t);    getnext();    kmp();    if(bz)cout<<"NO";    return 0;}

哈希版（unsigned long long会自然溢出，相当于mod一个数，所以基数可用适当大的素数避免冲突）

#include<iostream>#include<cstdio>#include<cstring>#include<string>#include<algorithm>using namespace std;const int N=1e6+5,base=61;char s[N],t[N];int sn,tn;unsigned long long num,bin[N],hash[N];int main(){    //freopen("lx.in","r",stdin);    scanf("%s%s",s+1,t+1);    sn=strlen(s+1),tn=strlen(t+1);    for(int i=tn;i>=1;i--)num=num*base+t[i]-'a';    for(int i=sn;i>=1;i--)hash[i]=hash[i+1]*base+s[i]-'a';    bin[0]=1;    for(int i=1;i<=tn;i++)bin[i]=bin[i-1]*base;    int bz=1;    for(int i=1;i<=sn-tn+1;i++)    {        if(hash[i]-hash[i+tn]*bin[tn]==num)        {            bz=0;            cout<<i<<endl;        }    }    if(bz)cout<<"NO";    return 0;   }