HDU - 1711 Number Sequence

最新推荐文章于 2019-05-20 18:33:28 发布

The__sea

最新推荐文章于 2019-05-20 18:33:28 发布

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分类专栏： KMP

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本文详细介绍KMP算法原理及其实现过程，并通过一个具体的编程问题来演示如何使用KMP算法解决问题。文章包括了KMP算法的核心思想、next数组的构建方法以及KMP匹配过程的代码实现。

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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

ps: KMP经典题型，学过的都会写，如果没学过那就推荐看JULY大神的一篇博客：点击打开链接

讲解的很详细。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int a[1000010], b[10010];
int next[10010];
int n1,m1,n,m;
int Kmp(int* a, int n, int* b, int m) 
{
    int i = 0, j = 0;
    while(i < n) 
	{
        if(j == -1 || a[i] == b[j])
		 {
            ++i; 
			++j;
            if(j == m) 
			{
                return i - m + 1;
            }
        }
        else 
		{
            j = next[j];
        }
    }
    return -1;
}
void getnext(int* b, int m) 
{
    int i = 0, j = 0;
    next[0] = -1; j = next[i];
    while(i < m) 
	{
        if(j == -1 || b[i] == b[j])
		 {
            next[++i] = ++j;
        }
        else 
		{
            j = next[j];
        }
    }
}
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 i=0;i<m;i++)
		  scanf("%d",&b[i]);
		  
		getnext(b, m);   
          printf("%d\n", Kmp(a, n, b, m));
	}
    return 0;
}