KMPc++实现

#include<iostream>
#include<cstring>
#include<algorithm>

using namespace std;


void getNextArray(char* str2,int* next)
{
    int len = strlen(str2);
    next[0] = -1;
    next[1] = 0;
    int pos = 2;
    int cn = 0;

    while(pos < len)
    {
        if(str2[pos -1] == str2[cn])
        {
            next[pos++] = ++cn;
        }
        else if(cn > 0)
        {
            cn = next[cn];
        }
        else
            next[pos++] = 0;
    }
}

int kmp(char* str1,char *str2,int * next)
{
    int len1 = strlen(str1);
    int len2 = strlen(str2);
    int i1 = 0;
    int i2 = 0;
    getNextArray(str2,next);
    while(i1 < len1 && i2 < len2)
    {
        if(str1[i1] == str2[i2])
        {
        i1++;
        i2++;
        }
        else if (next[i2] == -1)
        {
        i1++;
        }
        else
        {
        i2 = next[i2];
        }
    }
    return i2 == len2 ? i1 -i2 : -1;

}

int main()
{
    char str1[] = "12a12abc12";
    char str2[] = "12ab";
    int next[strlen(str2)];
    cout << kmp(str1,str2,next) << endl;
    return 0;
}