KMP详解

最新推荐文章于 2024-10-26 18:34:56 发布

Allen_0526

最新推荐文章于 2024-10-26 18:34:56 发布

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分类专栏： KMP 文章标签： KMP

本文链接：https://blog.youkuaiyun.com/qq_38984851/article/details/84639119

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本文深入解析了KMP算法的原理与实现，通过具体示例讲解如何在两组数列中查找匹配子序列，提供了完整的C++代码实现，并探讨了算法在字符串搜索等场景的应用。

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KMP详解
A - Number Sequence
Description

Given 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.

Input

The 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].

Output

For each test case, you should output one line which only contain K described above. If no such K exists, output -1 instead.

Sample Input

2
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 Output

6
-1

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <queue>
#include <set>
#include <map>
#define PI acos(-1)
const int mod = 1001113;
const int maxx = 1e6 + 10;
typedef long long LL;
using namespace std;
LL a[2000010],b[2000010],nex[2000010],i,j;
LL n,m,k;
int kmp()
{
    i=0;
    j=0;
    while(i<m&&j<n)
    {
        if(j==-1 || a[i]==b[j])
        {
            i++;
            j++;
        }
        else
            j=nex[j];
    }
    if(j==n)
        return i-j+1;
    else
        return -1;
}
void next()
{
    i=0,j=-1;
    nex[0]=-1;
    while(i<n)
    {
        if(j==-1||b[i]==b[j])
            nex[++i]=++j;
        else
            j=nex[j];
    }
}
int main()
{
    LL t;
    cin>>t;
    while(t--)
    {
        cin>>m>>n;
        for(LL i=0;i<m;i++)
            cin>>a[i];
        for(LL i=0;i<n;i++)
            cin>>b[i];
        next();
        k=kmp();
        cout<<k<<endl;
    }
    return 0;
}