[kuangbin带你飞]专题十六 KMP & 扩展KMP & Manacher A - Number Sequence HDU - 1711 (kmp)

小鱼儿 2023-08-17 15:41 101阅读 0赞

### \[kuangbin带你飞\]专题十六 KMP & 扩展KMP & Manacher ###

## A - Number Sequence ##

###  HDU - 1711 ###

题目链接：[https://vjudge.net/contest/70325\#problem/A][https_vjudge.net_contest_70325_problem_A]

题目：

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.

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 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
    题意：给你两个序列a,b，找出b序列在a中出现的位置，利用kmp算法

//
    // Created by hanyu on 2019/8/13.
    //
    
    #include <algorithm>
    #include <iostream>
    #include <cstdio>
    #include <cstring>
    #include <queue>
    #include <set>
    #include<math.h>
    #include<map>
    using namespace std;
    typedef long long ll;
    const int maxn=1e6+7;
    #define MAX 0x3f3f3f3f
    int a[maxn],b[maxn];
    int nextt[maxn];
    int n,m;
    void getnext()
    {
        int i=0,j=-1;
        nextt[0]=-1;
        while(i<m) {
            if (j == -1 || b[i] == b[j]) {
                i++, j++;
                if (b[i] != b[j])
                    nextt[i] = j;
                else
                    nextt[i] = nextt[j];
            } else
                j = nextt[j];
        }
    }
    int kmp()
    {
        int i=0,j=0;
        while(i<n&&j<m)
        {
            if(j==-1||a[i]==b[j])
            {
                i++,j++;
            } else
                j=nextt[j];
        }
        if(j==m)
            return i-j+1;
        return -1;
    }
    int main()
    {
        int T;
        scanf("%d",&T);
        while(T--)
        {
            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]);
            getnext();
            if(n<m)
                printf("-1\n");
            else
                printf("%d\n",kmp());
        }
        return 0;
    }

转载于:https://www.cnblogs.com/Vampire6/p/11348481.html

[https_vjudge.net_contest_70325_problem_A]: https://vjudge.net/contest/70325#problem/A