利用KMP算法匹配一个串T在另一个串S中首次出现的位置,套模板即可。
代码如下:
#include <bits/stdc++.h>
using namespace std;
const int N = 1000005;
int S[N], T[N]; // 下标从0开始
int lens, lent;
int Next[N]; // 下标从1开始
void getNext()
{
int i = 0;
int k = -1;
Next[0] = -1;
while (i < lent)
if (k == -1 || T[i] == T[k])
Next[++i] = ++k;
else
k = Next[k];
}
int KMP_index()
{
int i = 0;
int j = 0;
getNext();
while (i < lens && j < lent)
{
if (j == -1 || S[i] == T[j])
{
i++;
j++;
}
else
j = Next[j];
}
if (j == lent)
return i - lent + 1; // 输出的答案下标从1开始,所以要+1
else
return -1;
}
int main()
{
//freopen("test.txt", "r", stdin);
//freopen("out.txt", "w", stdout);
int t;
scanf("%d", &t);
while(t--)
{
scanf("%d%d", &lens, &lent);
for (int i = 0; i < lens; i++)
scanf("%d", &S[i]);
for (int i = 0; i < lent; i++)
scanf("%d", &T[i]);
printf("%d\n", KMP_index());
}
return 0;
}