hdu 1711Number Sequence(kmp模板题)

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本博客介绍了一个使用KMP算法解决的问题，即在给定的两个序列中找到第二个序列在第一个序列中最早完全匹配的位置。通过提供示例输入和输出，详细解释了解决思路和代码实现。

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Number Sequence

Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 19127 Accepted Submission(s): 8218

Problem 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

Source

HDU 2007-Spring Programming Contest

题意:给你n,m(1 <= M <= 10000, 1 <= N <= 1000000),接下来分别是长度为n和m的两个数组,求第二个数组在第一个数组中最先被完全匹配的位置。

思路:kmp模板题.当第二个数组匹配到位置m时,只要输出此时第一个数组此时的位置-m+1便可以了.

#include<bits/stdc++.h>
using namespace std;
const int maxn=1100000;
int n,m;
int pattern[maxn],s[maxn];
int Next[maxn];

void get_next(){
    int i=0,j=-1;
    Next[0]=-1;
    while(i<m){
        if(j==-1||pattern[j]==pattern[i]){
            j++,i++;
            Next[i]=j;
        }
        else
            j=Next[j];
    }
}

void Kmp(){
    int i=0,j=0,flag=0;
    while(i<n){
        if(j==-1||s[i]==pattern[j])
            i++,j++;
        else
            j=Next[j];
        if(j==m){
            printf("%d\n",i+1-m);
            flag=1;
            break;
        }
    }
    if(flag==0)
        printf("-1\n");
}

int main(){
    int _;
    scanf("%d",&_);
    while(_--){
        scanf("%d%d",&n,&m);
        for(int i=0;i<n;i++)
            scanf("%d",&s[i]);
        for(int i=0;i<m;i++)
            scanf("%d",&pattern[i]);
        get_next();
        Kmp();
    }
    return 0;
}