KMP算法c++代码

先放代码，对着代码来讲一讲（代码没加注释）

#include<iostream>

#include<string.h>
const int MAXLEN = 50;
int next[MAXLEN] = { 0 };
int nextval[MAXLEN] = { 0 };

void get_next(char s[],int lens)
{
	int j = 0;
	int k = -1;
	next[j] = k;
	while (j < lens-1)
	{
		if (k == -1 || s[j] == s[k])
		{
		    k++;
		    j++;
		    next[j] = k;
		}
		else
		    k = next[k];
	}
}

int main()
{
	char strings[] = "hello worldolollo,I'm the king of the world,and you'll be die!";
	char pattern[] = "olol";
	int lens = strlen(strings);
	int lenpatt = strlen(pattern);
	get_next(pattern, lenpatt);
	int i = 0, j = 0;
	while (i < lens&&pattern[j]!='\0')
	{
		if (j == -1 || strings[i] == pattern[j])
		{
			i++;
			j++;
		}
		else
		{
			j = next[j];
		}
	}
	if (pattern[j] == '\0')
		printf("%d\n", i - lenpatt);
	else
		printf("not found\n");
		return 0;
}

1、kmp算法的核心就是减少不必要的回溯，也就是说，我们在匹配到中间某个字符发现失配的时候，不需要重头再来（回忆太累人了你说是吧），我们已经在过程中有了很多线索，这