HDU - 1711 Number Sequence（KMP）

#include <cstdio>
#include <cstring>
const int N = 1000010;
int a
, b
, next
;
int n, m;
void init() {
scanf("%d%d", &n, &m);
for (int i = 1; i <= n; i++)
scanf("%d", &a[i]);

for (int j = 1; j <= m; j++)
scanf("%d", &b[j]);
}

void getFail() {
next[1] = 0;
int i = 1, j = 0;
while (i <= m) {
if (j == 0 || b[i] == b[j]) {
j++; i++;
next[i] = j;
}
else j = next[j];
}
}

int solve() {
getFail();
int i = 1, j = 1;
while (i <= n) {
if (j == 0 || a[i] == b[j]) {
i++; j++;
if (j == m + 1) return i - m;
}
else j = next[j];
}
return -1;
}

int main() {
int test;
scanf("%d", &test);
while (test--) {
init();
printf("%d\n", solve());
}
return 0;
}