Number Sequence HDU - 1711 （KMP）

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

题目大意：就是让你在第一个数组中找与第二个数组匹配的位置。

解题思路：因为是要最小的位置k，所以用kmp跑一遍，只要当第二数组跑到其长度停止。返回此时在第一个数组的位置，最后判断存不存在即可。

有一点，如果要用c++写的话需要关闭输入输出流，否则超时。。

/*
@Author: Top_Spirit
@Language: C++
*/
//#include <bits/stdc++.h>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std ;
typedef unsigned long long ull ;
typedef long long ll ;
const int Maxn = 1e6 + 10 ;
const int INF = 0x3f3f3f3f ;
const double PI = acos(-1.0) ;
const ull seed = 133 ;

int n, m ;
int Next[Maxn] ;
int a[Maxn], b[Maxn] ;

void getNext(){
    Next[0] = -1 ;
    int j = 0, k = -1 ;
    while (j < m){
        if (k == -1 || b[j] == b[k]) Next[++j] = ++k ;
        else k = Next[k] ;
    }
}

int KMP (){
    int i = 0, j = 0 ;
    while (i < n){
        if (j == -1 || a[i] == b[j]){
            i++ ;
            j++ ;
        }
        else j = Next[j] ;
        if (j == m) return i ;
    }
    return -1 ;
}

int main (){
    ios_base :: sync_with_stdio(false) ;
    cin.tie(0) ;
    cout.tie(0) ;
    int T ;
    cin >> T ;
    while (T--){
        cin >> n >> m ;
        for (int i = 0; i < n; i++) cin >> a[i] ;
        for (int i = 0; i < m; i++) cin >> b[i] ;
        getNext() ;
        int ans = KMP() ;
        if (ans == -1) cout << -1 << endl ;
        else  cout << ans - m  + 1 << endl ;
    }
    return 0 ;
}

Number Sequence HDU - 1711 （KMP）

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