loj103 子串查找（kmp/Hash模板题）

KMP模板题

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
#define ll long long
#define inf 0x3f3f3f3f
#define N 1000010
inline int read(){
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();
    return x*f;
}
int n,m,fail[N],ans=0;
char s[N],t[N];
inline void getfail(){
    int k=0;fail[1]=0;
    for(int i=2;i<=m;++i){
        while(k&&t[k+1]!=t[i]) k=fail[k];
        if(t[k+1]==t[i]) ++k;fail[i]=k;
    }
}
int main(){
//  freopen("a.in","r",stdin);
    scanf("%s%s",s+1,t+1);
    n=strlen(s+1);m=strlen(t+1);
    getfail();int k=0;
    for(int i=1;i<=n;++i){
        while(k&&t[k+1]!=s[i]) k=fail[k];
        if(t[k+1]==s[i]) ++k;if(k==m) ++ans;
    }printf("%d\n",ans);
    return 0;
}

顺手复习hash了

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
#define ll long long
#define inf 0x3f3f3f3f
#define N 1000010
#define ull unsigned long long
#define k1 11113
inline int read(){
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();
    return x*f;
}
char s[N];
int n,m,ans=0;
ull hs[N],hst,binm;
int main(){
//  freopen("a.in","r",stdin);
    scanf("%s",s+1);n=strlen(s+1);
    for(int i=1;i<=n;++i) hs[i]=hs[i-1]*k1+s[i];
    scanf("%s",s+1);m=strlen(s+1);binm=1;
    for(int i=1;i<=m;++i) hst=hst*k1+s[i],binm*=k1;
    for(int i=m;i<=n;++i){
        if(hs[i]-hs[i-m]*binm==hst) ++ans;
    }printf("%d\n",ans);
    return 0;
}