KMP算法的实现

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void GetNext(const char *sub, int *next)
{
	int slen = strlen(sub);
	int k = 0;
	next[0] = 0;

	for (int i = 1; i < slen; ++i)
	{
		while (k > 0 && sub[i] != sub[k])
			k = next[k-1];

		if (sub[i] == sub[k])
			k++;

		next[i] = k; 
	}
}

int KmpSearch(const char *src, const char *sub)
{
	int k = 0;
	int n, m;
	n = strlen(src);
	m = strlen(sub);

	int *next = (int *)malloc(sizeof(int)*m);

	GetNext(sub, next);

	for (int i = 0; i < n; ++i)
	{
		while (k > 0 && src[i] != sub[k])
			k = next[k-1];

		if (src[i] == sub[k])
			k++;

		if (k == m)
		{
			delete [] next;
			return (i - m + 1);
		}
	}
	delete [] next;
	return -1;
}

int main()
{
	char src[] = "ABCDEABDE";
	char sub[] = "ABD";

	printf("%s中，第一次出现%s子串的下标为：%d\n", src, sub, KmpSearch(src, sub));
	return 0;
}