kmp复习

http://vjudge.net/contest/view.action?cid=47286#problem/A

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

     
     
     
     

      
      
      
       2
13 5
1 2 1 2 3 1 2 3 1 3 2 1 2
1 2 3 1 3
13 5
1 2 1 2 3 1 2 3 1 3 2 1 2
1 2 3 2 1 
     
     
     
     

 

Sample Output

     
     
     
     

      
      
      
       6
-1 
     
     
     
     

 

#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <iostream>
using namespace std;
const int N=1000002;
int a[N],next[N/100+2];
int b[N/100+2],m,n;
void get_next()
{
    int i,j;
    next[0]=j=-1;
    for(i=1;i<m;i++)
    {
        while(j>-1&&b[i]!=b[j+1])
            j=next[j];
        if(b[i]==b[j+1])
             j++;
        next[i]=j;
    }
}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d%d",&n,&m);
        for(int i=0;i<n;i++)
           scanf("%d",&a[i]);
        for(int i=0;i<m;i++)
           scanf("%d",&b[i]);
        get_next();
        int j=-1,ip=0;
        int flag=1;
        for(int i=0;i<n;i++)
        {
            while(j>-1&&a[i]!=b[j+1])
            {
               j=next[j];
            }
            if(a[i]==b[j+1])
               j++;
            if(j==m-1)
            {
                flag=0;
                ip=i-j+1;
                break;
            }
        }
        if(flag==0)
           printf("%d\n",ip);
        else
          printf("-1\n");
    }
    return 0;
}