KMP分为两部分，一部分为匹配，一部分寻找next,
寻找next

void getNext( )
{
    Next[0] = -1;
    int i = 0, j = -1;
    int len=strlen(p);
    while (i < len)
    {
        if (j == -1 || p[i] == p[j])
        {
            ++i;
            ++j;
            Next[i] = j;
        }   
        else
            j = Next[j];
    }
}

匹配

void KMP( ) 
{
    int i = 0; 
    int j = 0;
     int len1=strlen(t);
    int len2=strlen(p);
    while (i < len1 && j < len2)
    {
        if (j == -1 || t[i] == p[j]) 
        {
                i++;
                j++;

        }
        else j = Next[j];
    }

    if (j == len2)
       cout<<i-j+1<<endl;
    else 
       cout<<"::>_<::"<<endl;
}