Problem DescriptionGiven two sequences of numbers : a[1], a[2], ...... , a[N], and b[1], b[2], ...... , b[M] (1 <= M <= 10000, 1 <= N <= 1000000). Your task is to find a number K which make a[K] = b[1], a[K + 1] = b[2], ...... , a[K + M - 1] = b[M]. If there are more than one K exist, output the smallest one. InputThe first line of input is a number T which indicate the number of cases. Each case contains three lines. The first line is two numbers N and M (1 <= M <= 10000, 1 <= N <= 1000000). The second line contains N integers which indicate a[1], a[2], ...... , a[N]. The third line contains M integers which indicate b[1], b[2], ...... , b[M]. All integers are in the range of [-1000000, 1000000]. OutputFor each test case, you should output one line which only contain K described above. If no such K exists, output -1 instead. Sample Input2 13 5 1 2 1 2 3 1 2 3 1 3 2 1 2 1 2 3 1 3 13 5 1 2 1 2 3 1 2 3 1 3 2 1 2 1 2 3 2 1 Sample Output6 -1 思路:字符串匹配,使用kMP算法(详情见博客:https://mp.csdn.net/postedit) AC代码: |
#include<stdio.h>
int a[1000001],b[10001],Next[100001]; //求Next数组
void getNext(int m)
{
int i=0,j=-1;
Next[0]=-1;
while(i<m){
if(j==-1||b[i]==b[j]){
i++;j++;
Next[i]=j;
}
else
j=Next[j];
}
return ;
}
int main()
{
int t;
scanf("%d",&t);
while(t--)
{
int m,n;
scanf("%d%d",&n,&m);
for(int i=0;i<n;i++)
scanf("%d",&a[i]);
for(int j=0;j<m;j++)
scanf("%d",&b[j]);
int k=0,s=0;
getNext(m);
while(k<n&&s<m)
{
if(a[k]==b[s]||s==-1){
k++;s++;
}
else{
s=Next[s];
}
if(s==m){
printf("%d\n",k-s+1);
break;
}
}
if(s!=m)
printf("-1\n");
}
return 0;
}