HDU 1711 Number Sequence

#include <iostream>
#include <queue>
using namespace std ;
int n,m;
int a[1000002],b[10002];
int _next[1000002];
void Init_()
{
int i,k;
i = 0; k = -1; _next[0] = -1;
while(i < m){
if(k == -1 || b[i] == b[k]){
i++;k++;
if(b[i] != b[k])
_next[i] = k;
else
_next[i] = _next[k];
}
else
k = _next[k];
}
}
int kmp()
{
int i,j;
i = 0;j = 0;
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;
return -1;
}
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]);
Init_();
printf("%d\n",kmp());
}
return 0;
}