裸kmp算法

Number Sequence

[align=left]Problem Description[/align]
Given two sequences of numbers : a[1], a[2], ...... , a
, 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.

[align=left]Input[/align]
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
. The third line contains M integers which indicate b[1], b[2], ...... , b[M]. All integers are in the range of [-1000000, 1000000].

[align=left]Output[/align]
For each test case, you should output one line which only contain K described above. If no such K exists, output -1 instead.

[align=left]Sample Input[/align]

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

[align=left]Sample Output[/align]

6
-1

刚接触kmp还不是很理解，next失效函数

#include <iostream>
#include <cstdio>
using namespace std;
int f[10001];
int n,m;
int a[1000001],b[10001];
int kmp(int t[],int p[])
{
int i=0,j=0;
while(i<n&&j<m)
{
if(j==-1||t[i]==p[j])
{
i++;
j++;
}
else
j=f[j];
}
if(j>=m)
return i-m+1;
return -1;
}
void next(int p[])
{
int k=-1,j=0;
f[0]=-1;
while(j<m)
{
if(k==-1||p[k]==p[j])
{
k++;
f[++j]=k;
}
else
k=f[k];
}
}
int main()
{
int T,i,j;
//freopen("in.txt","r",stdin);
cin>>T;
while(T--)
{
cin>>n>>m;
for(i=0;i<n;i++)
cin>>a[i];
for(i=0;i<m;i++)
cin>>b[i];
next(b);
cout<<kmp(a,b)<<endl;
}
}