KMP

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

#include<iostream>
using namespace std;
int nx[10000+5], b[10000+5], a[1000000+5];
int n, m;
void getnext(){
    int k = -1, j = 0;
    nx[0] = -1;
    while(j < m){
        if(k == -1 || b[j] == b[k]) nx[++j] = ++k;
        else k = nx[k];
    }
}
int KMP()
{
    int flag = -1;
    for(int i = 0, j = 0; i < n; i++){
        while(j > 0 && b[j] != a[i]) j = nx[j];
        if(a[i] == b[j]) j++;
        if(j == m)
        {
            return i - j + 2;
        }
    }
    return -1;
}
int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t;
    cin >> t;
    while(t--){
        cin >> n >> m;
        for(int i = 0; i < n; i++) cin >> a[i];
        for(int i = 0; i < m; i++) cin >> b[i];
        getnext();
        cout << KMP() << endl;
    }
    return 0;
}