poj 3461 字串單串匹配--KMP或者字串HASH

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http://poj.org/problem?id=3461

先來一發KMP演算法：

#include <cstdio>#include <cstring>#include <algorithm>#include <string>#include <iostream>#include <cmath>#include <map>#include <queue>using namespace std;#define ls(rt) rt*2#define rs(rt) rt*2+1#define ll long long#define ull unsigned long long#define rep(i,s,e) for(int i=s;i<e;i++)#define repe(i,s,e) for(int i=s;i<=e;i++)#define CL(a,b) memset(a,b,sizeof(a))#define IN(s) freopen(s,"r",stdin)#define OUT(s) freopen(s,"w",stdin)const int MAXN = 1000000+100;char T[MAXN],P[MAXN],tmp[MAXN];//T--文本，P--模板串int fail[MAXN];void getfail(){    int m=strlen(P);    fail[0]=fail[1]=0;    for(int i=1;i<m;i++)    {        int j=fail[i];        while(j && P[i]!=P[j])j=fail[j];        fail[i+1]=P[i]==P[j]?j+1:0;    }}int Find(){    int ans=0;    int n=strlen(T),m=strlen(P);    if(n<m)    {        strcpy(tmp,T);        strcpy(T,P);        strcpy(P,tmp);    }    getfail();    int j=0;    for(int i=0;i<n;i++)    {        while(j && P[j]!=T[i])j=fail[j];        if(P[j] == T[i])j++;        if(j==m)//printf("%d\n",i-m+1);//find it            ans++;    }    return ans;}int main(){    //IN("poj3461.txt");    int n;    while(~scanf("%d",&n))    {        while(n--)        {            scanf("%s%s",P,T);            printf("%d\n",Find());        }    }    return 0;}

再來一發字串HASH

我的字串HASH模板在http://blog.csdn.net/u011026968/article/details/38460357

#include <cstdio>#include <cstring>#include <algorithm>#include <string>#include <iostream>#include <cmath>#include <map>#include <queue>using namespace std;#define ls(rt) rt*2#define rs(rt) rt*2+1#define ll long long#define rep(i,s,e) for(int i=s;i<e;i++)#define repe(i,s,e) for(int i=s;i<=e;i++)#define CL(a,b) memset(a,b,sizeof(a))#define IN(s) freopen(s,"r",stdin)#define OUT(s) freopen(s,"w",stdin)#define ull unsigned long longconst ull B = 1e8+7;    /*according to the book*/const int MAXN = 1000000+100;char a[MAXN],b[MAXN],tmp[MAXN];int hashfind(){    int ans=0;    int al=strlen(a),bl=strlen(b);    if(al>bl)    {        strcpy(tmp,a);        strcpy(a,b);        strcpy(b,tmp);    }    ull t=1,ah=0,bh=0;    for(int i=0;i<al;i++)    {        t*=B;        ah=ah*B+a[i];        bh=bh*B+b[i];    }    for(int i=0;i+al<=bl;i++)    {        if(ah==bh)ans++;        if(i+al<bl)bh=bh*B+b[i+al]-b[i]*t;    }    return ans;}int main(){    //IN("poj3461.txt");    int n;    while(~scanf("%d",&n))    {        while(n--)        {            scanf("%s%s",a,b);            printf("%d\n",hashfind());        }    }    return 0;}