HDU1711 Number Sequence KMP

HDU1711 Number Sequence

/*KMP字符串匹配
1341MS	9368K
*/
#include <stdio.h>
#include <string.h>
const int MAX=1e6+5;
int str1[MAX],str2[MAX];
int next[MAX];
void read(int &x)//读入优化
{
    int f=1;x=0;char s=getchar();
    while(s<'0'||s>'9'){if(s=='-')f=-1;s=getchar();}
    while(s>='0'&&s<='9'){x=x*10+s-'0';s=getchar();}
    x*=f;
}
void buildnext(int m)//建立next数组
{
    next[0]=-1;
    for (int k=1,i=-1;k<m;k++)
    {
        while (str2[i+1]!=str2[k]&&i!=-1) i=next[i];
        if (str2[i+1]==str2[k]) i++;
        next[k]=i;
    }
}
int KMPfind(int n,int m)//KMP匹配
{
    buildnext(m);
    for (int k=0,i=-1;k<n;k++)
    {
        while (str2[i+1]!=str1[k]&&i!=-1) i=next[i];
        if (str2[i+1]==str1[k]) i++;
        if (i==m-1) return k-m+2;//return 第一个
    }
    return -1;
}
int main ()
{

    int T,n,m;
    read(T);
    while (T--)
    {
        memset(next,0,sizeof(next));
        read(n);read(m);
        for (int k=0;k<n;k++)
            read(str1[k]);
        for (int k=0;k<m;k++)
            read(str2[k]);
        printf ("%d\n",KMPfind(n,m));
    }
    return 0;
}