字符串模板汇总

字符串模板

KMP

#include<iostream>
#include<cstring>
#include<cstdio>

using namespace std;

const int MAXN=1000010;

int n,m,next[MAXN];
char a[MAXN],b[MAXN];	//a为主串，b为模式串 

int main(){
	scanf("%s%s",a+1,b+1);
	n=strlen(a+1),m=strlen(b+1);
	int j=0;
	next[1]=0;
	for(int i=1;i<m;++i){
		while(j&&b[j+1]!=b[i+1]) j=next[j];
		if(b[j+1]==b[i+1]) ++j;
		next[i+1]=j;
	}
	j=0;
	for(int i=0;i<n;++i){
		while(j&&b[j+1]!=a[i+1]) j=next[j];
		if(b[j+1]==a[i+1]) ++j;
		if(j==m){
			printf("%d\n",i-j+2);	//字符串a的第(i+1)-j+1个字母开头的字符与b匹配 
			j=next[j];
		}
	}
	for(int i=1;i<=m;++i)
		printf("%d ",next[i]);
	puts("");
	return 0;
}

manacher

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;

const int MAXN=22000010;

int n,p[MAXN];
char s[MAXN],a[MAXN];

int main(){
	scanf("%s",s+1);
	n=strlen(s+1);
	a[0]='$';
	for(int i=1;i<=n;++i)
		a[i*2-1]='$',a[i*2]=s[i];
	a[n*2+1]='$';
	n=n*2+1;
	int k=0,mx=0;
	for(int i=1;i<=n;++i){
		if(i<=mx) p[i]=min(mx-i,p[k*2-i]);
		while(a[i+p[i]+1]==a[i-p[i]-1]) ++p[i];
		if(i+p[i]>mx) mx=i+p[i],k=i;
	}
	int Ans=0;
	for(int i=1;i<=n;++i)
		Ans=max(Ans,p[i]);
	printf("%d\n",Ans);
	return 0;
}

哈希字符串匹配

#include<iostream>
#include<cstring>
#include<cstdio>

#define LL long long

using namespace std;

const int MAXN=1000010;
const int MOD=1e9+7; 
const int Base=27;

int n,m,nxt[MAXN];
char s1[MAXN];	//主串 
char s2[MAXN];	//模式串

LL Hash[MAXN],p[MAXN],hashs2;

LL get_Hash1(int l,int r){
	return (Hash[r]-Hash[l-1]*p[r-l+1]%MOD+MOD)%MOD;
}

int main(){
	scanf("%s",s1);
	scanf("%s",s2);
	n=strlen(s1);
	m=strlen(s2);
	p[0]=1;
	for(int i=0;i<n;++i){
		Hash[i]=(Hash[i-1]*Base+s1[i]-'A'+1)%MOD;
		p[i+1]=p[i]*Base%MOD;
	}
	for(int i=0;i<m;++i)
		hashs2=(hashs2*Base+s2[i]-'A'+1)%MOD;

	for(int i=0;i+m-1<n;++i){
		if(get_Hash1(i,i+m-1)==hashs2){
			printf("%d\n",i+1);
		}
	}
	return 0;
}

双哈希字符串查重

#include<iostream>
#include<cstring>
#include<cstdio>
#include<map> 
using namespace std;

#define LL long long

const int MAXN = 10010;
const int MAXM = 1510;
const int Base = 79;
const int MOD1 = 1e9+9;
const int MOD2 = 1e9+7;

int get_num(char x){
	if('A'<=x&&x<='Z') return x-'A';
	else if('a'<=x&&x<='z') return x-'a'+26;
	else return x-'0'+52; 
}

int n,cnt;
map<int,bool> Hash;
char s[MAXM];

int main(){
	scanf("%d",&n);
	for(int i=1;i<=n;++i){
		scanf("%s",s);
		int len=strlen(s);
		LL ha1=0ll,ha2=0ll;
		for(int i=0;i<len;++i){
			ha1=(ha1*Base+get_num(s[i]))%MOD1;
			ha2=(ha2*Base+get_num(s[i]))%MOD2;
		}
		if(!Hash[ha1]&&!Hash[ha2]){
			++cnt;
			Hash[ha1]=Hash[ha2]=1;
		}
	}
	printf("%d\n",cnt);
	return 0;
}

trie

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;

const int MAXN=3000010;

int T,n,q,num,ch[MAXN][65],cnt[MAXN];

inline int get_num(char x){
	if('A'<=x&&x<='Z') return x-'A';
	else if('a'<=x&&x<='z') return x-'a'+26;
	else return x-'0'+52; 
}

void insert(char s[]){
	int l=strlen(s);
	int p=0;
	for(int i=0;i<l;++i){
		int c=get_num(s[i]);
		if(!ch[p][c]) ch[p][c]=++num;
		p=ch[p][c];
		++cnt[p];
	}
}

int query(char s[]){
	int l=strlen(s);
	int p=0;
	for(int i=0;i<l;++i){
		int c=get_num(s[i]);
		if(!ch[p][c]) return 0;
		p=ch[p][c];
	}
	return cnt[p];
}

int main(){
	scanf("%d",&T);
	while(T--){
		for(int i=0;i<=num;++i){
			for(int j=0;j<63;++j)
				ch[i][j]=0;
			cnt[i]=0;
		}
		num=0;
		scanf("%d%d",&n,&q);
		char s[MAXN];
		for(int i=1;i<=n;++i){
			scanf("%s",s);
			insert(s);
		}
		for(int i=1;i<=q;++i){
			scanf("%s",s);
			printf("%d\n",query(s));
		}
	}
	return 0;
}

AC自动机

#include<iostream>
#include<cstring>
#include<cstdio>

#define rep(i,l,r) for(int i=l;i<=r;i++)
#define reset(a) memset(a,0,sizeof(a))
#define MAXN 20010

using namespace std;

int ch[MAXN][26],next[MAXN],mark[MAXN];
int sum[MAXN],que[MAXN<<5],pos[MAXN];
int n,cnt=1,head,tail,maxx;
char s[155][155];

void insert(char ss[],int p){
	int u=1,len=strlen(ss);
	rep(i,0,len-1){
		int c=ss[i]-'a';
		if(!ch[u][c]) ch[u][c]=++cnt;
		u=ch[u][c];
	}
	mark[u]++; pos[p]=u;
}

void bfs(){
	head=tail=0;
	rep(i,0,25) ch[0][i]=1;
	que[++tail]=1; next[1]=0;
	while(head<tail){
		int u=que[++head];
		rep(i,0,25){
			if(!ch[u][i])
				ch[u][i]=ch[next[u]][i];
			else{
				que[++tail]=ch[u][i];
				next[ch[u][i]]=ch[next[u]][i];
			}
		}
	}
}

void find(char ss[]){
	int u=1,len=strlen(ss),c,k;
	rep(i,0,len-1){
		c=ss[i]-'a';
		k=ch[u][c];
		while(k>1){
			if(mark[k]){
				sum[k]++;
				if(sum[k]>maxx)
					maxx=sum[k];
			}k=next[k];
		}
		u=ch[u][c];
	}
}

int main(){
	scanf("%d",&n);
	char S[1000100];
	while(n){
		reset(ch); reset(next);
		reset(sum); reset(mark);
		reset(pos); cnt=1; maxx=0;
		for(int i=1;i<=n;i++){
	 		scanf("%s",s[i]);
	 		insert(s[i],i);
		}
		scanf("%s",S);
		bfs();
		find(S);
		printf("%d\n",maxx);
		for(int i=1;i<=n;i++)
		 if(sum[pos[i]]==maxx)
		  printf("%s\n",s[i]);
		scanf("%d",&n);
	}
	return 0;
}