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

KMP 的模板题．

关于KMP，先看这个视频：https://www.bilibili.com/video/av3246487/

理解KMP的过程，再去学怎么码代码．

#include <cstdio>
using namespace std;
int n, m;
int a[1000005], b[10005];
int next[10005];
void get_next()
{
    next[0] = -1;
    int i = 0, j = -1;
    while (i < m) {
        if (j == -1 || b[j] == b[i]) {
            next[++i] = ++j;
        } else {
            j = next[j];
        }
    }
}
int kmp()
{
    int i = 0, j = 0, ans = -1;
    get_next();
    while (i < n) {
        if (j == -1 || a[i] == b[j]) {
            i++, j++;
        } else {
            j = next[j];
        }
        if (j == m) {
            ans = i - m + 1;
            break;
        }
    }
    return ans;
}
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);
        printf("%d\n", kmp());
    }
    return 0;
}