hdu1711 Number Sequence (KMP)

http://acm.hdu.edu.cn/showproblem.php?pid=1711

Number Sequence

Problem Description

Given two sequences of numbers : a[1], a[2], ...... , a[N], and b[1], b[2], ...... , b[M] (1 <= M <= 10000, 1 <= N <= 1000000). Your task is to find a number K which make a[K] = b[1], a[K + 1] = b[2], ...... , a[K + M - 1] = b[M]. If there are more than one K exist, output the smallest one.

 

Input

The first line of input is a number T which indicate the number of cases. Each case contains three lines. The first line is two numbers N and M (1 <= M <= 10000, 1 <= N <= 1000000). The second line contains N integers which indicate a[1], a[2], ...... , a[N]. The third line contains M integers which indicate b[1], b[2], ...... , b[M]. All integers are in the range of [-1000000, 1000000].

 

Output

For each test case, you should output one line which only contain K described above. If no such K exists, output -1 instead.

 

Sample Input

213 51 2 1 2 3 1 2 3 1 3 2 1 21 2 3 1 313 51 2 1 2 3 1 2 3 1 3 2 1 21 2 3 2 1

 

Sample Output

6-1
用了两种方法做的，一种是直接用KMP,另一种是把Ａ[]和Ｂ[]连接，先要在Ｂ[]的末尾用一个大一点的数卡一下再连接，通过求next[]的时候即可判断；
求next[]的方式:
#include<iostream>#include<stdio.h>#include<string.h>using namespace std;const int maxn=1100009;int  next[maxn],n,m;int a[maxn],b[maxn];int ans;void getnext(){    int i=0,j=-1;    next[0]=-1;    while(i<=m+n)    {        if(j==-1||b[i]==b[j])            next[++i]=++j;        else j=next[j];        if(j==m)        {            ans=i-m-m;            break;        }    }}int main(){    int t,i;    scanf("%d",&t);    while(t--)    {        ans=-1;        scanf("%d%d",&n,&m);        for(i=0;i<n;i++)scanf("%d",&a[i]);        for(i=0;i<m;i++)scanf("%d",&b[i]);        b[m]=100000000;        for(i=0;i<n;i++)            b[i+m+1]=a[i];        getnext();        printf("%d\n",ans);    }    return 0;}
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直接KMP:
#include<iostream>#include<stdio.h>#include<string.h>using namespace std;const int maxn=1000009;int  next[10009],n,m;int a[maxn],b[10009];void getnext(){    int i=0,j=-1;    next[0]=-1;    while(i<m)    {        if(j==-1||b[i]==b[j])        {            i++;j++;             if(b[i]==b[j])next[i]=next[j];             else next[i]=j;        }        else j=next[j];    }}int kmp(){    int i=-1,j=-1;    while(i<n&&j<m)    {        if(j==-1||a[i]==b[j])        {            i++;j++;        }        else j=next[j];    }    if(j==m)        return i-m+1;    else return -1;}int main(){    int t,i;    scanf("%d",&t);    while(t--)    {        scanf("%d%d",&n,&m);        for(i=0;i<n;i++)scanf("%d",&a[i]);        for(i=0;i<m;i++)scanf("%d",&b[i]);        getnext();        printf("%d\n",kmp());    }    return 0;}