KMP算法模板 求子串和模板串首先匹配的位置

#include <cstdio>
using namespace std;

const int MAXN = 1e6 + 10;
int nex[MAXN];
int s[MAXN], t[MAXN];

void get_nex(int lm)    {
int i = 0, j = -1;   nex[0] = -1;
while (i < lm)  {
if (j == -1 || t[j] == t[i]) {
i++;    j++;    nex[i] = j;
}
else    j = nex[j];
}
}

int KMP(int ln, int lm)   {
get_nex (lm);
int i = 0, j = 0;
while (i < ln)  {
while (j != -1 && s[i] != t[j]) j = nex[j];
i++;    j++;
if (j == lm) return (i - j + 1);
}
return -1;
}

int main()    {
int T;
scanf ("%d", &T);
while (T--)   {
int ln, lm; scanf ("%d%d", &ln, &lm);
for (int i=0; i<ln; ++i)   scanf ("%d", &s[i]);
for (int i=0; i<lm; ++i)   scanf ("%d", &t[i]);
printf ("%d\n", KMP (ln, lm));
}

return 0;
}