HDU 1711 Number Sequence

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

#define maxn 1000050

int s1[maxn];
int s2[maxn];
int nnext[maxn];

void Getnext(int n2)
{
    int i=1;
    int j=0;
    nnext[i]=j;
    while(i<=n2)
    {
        if(j==0||s2[i]==s2[j])
            nnext[++i]=++j;
        else
            j=nnext[j];
    }
}

int Kmp(int n1,int n2)
{
    Getnext(n2);
    int i=1,j=1;
    while(i<=n1)
    {
        if(j==0||s1[i]==s2[j])
        {
            i++;
            j++;
        }
        else
            j=nnext[j];
        if(j==n2+1)
            return i-n2;
    }
    return -1;
}

int main()
{
    int t,n1,n2;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d%d",&n1,&n2);
        for(int i=1;i<=n1;i++)
            scanf("%d",&s1[i]);
        for(int i=1;i<=n2;i++)
            scanf("%d",&s2[i]);
        int ans=Kmp(n1,n2);
        printf("%d\n",ans);
    }

    return 0;
}