@ http://comeoncodeon.wordpress.com/2010/08/29/the-z-algorithm

bool zAlgorithm(string pattern, string target)
{
    string s = pattern + '$' + target ;
    int n = s.length();
    vector<int> z(n,0);
     
    int goal = pattern.length();
    int r = 0, l = 0, i;
    for (int k = 1; k<n; k++)
    {
        if (k>r)
        {
            for (i = k; i<n && s[i]==s[i-k]; i++);
            if (i>k)
            {
                z[k] = i - k;
                l = k;
                r = i - 1;
            }
        }
        else
        {
            int kt = k - l, b = r - k + 1;
            if (z[kt]>b)
            {
                for (i = r + 1; i<n && s[i]==s[i-k]; i++);
                z[k] = i - k;
                l = k;
                r = i - 1;
            }
        }
        if (z[k]==goal)
            return true;
    }
    return false;
}