朴素算法与KMP算法

朴素算法

#include <iostream>
using namespace std;

int BF(string s1, string s2, int pos)
{
	int i=pos;
	int j=0;
	while(i<s1.length() && j<s2.length())
	{
			if(s1[i] == s2[j])
			{
				i++;
				j++;
			}
			else
			{
				i = i-j+1;
				j = 0;
			}
	}
	
	if(j > s2.length()-1)
	{
		return i-j;
	}
	else
	{
		return -1;
	}
}

int main()
{
	string s1 = "appleisfriut";
	string s2 = "is";
	int pos = 0;
	int p = BF(s1,s2,pos);
	cout<<p<<endl;
}

KMP算法

void get_next(string str,int *next)
{
	int i,j;
	i=1;
	j=0;
	next[1]=0;
	while(i<str[0])
	{
		if(j==0 || str[i] == str[j])
		{
			++i;
			++j;
			next[i] = j;
		}
		else
			j = next[j];
	}
}

KMP算法主要是解决next数组的问题