// Introduction to Software Testing
// Authors: Paul Ammann & Jeff Offutt
// Chapter 2, section 2.3, page 56

class TestPat
{

public static void main (String []argv)
{
   final int MAX = 100;
   char subject[] = new char[MAX];
   char pattern[] = new char[MAX];
   if (argv.length != 2)
   {
      System.out.println
         ("java TestPat String-Subject String-Pattern");
      return;
   }
   subject = argv[0].toCharArray();
   pattern = argv[1].toCharArray();
   TestPat testPat = new TestPat ();
   int n = 0;
   if ((n = testPat.pat (subject, pattern)) == -1)
      System.out.println
      ("Pattern string is not a substring of the subject string");
   else
      System.out.println
      ("Pattern string begins at the character " + n);
}

public TestPat ()
{
}

public int pat (char[] subject, char[] pattern)
{
// Post: if pattern is not a substring of subject, return -1
//       else return (zero-based) index where the pattern (first)
//       starts in subject

   final int NOTFOUND = -1;
   int  iSub = 0, rtnIndex = NOTFOUND;
   boolean isPat  = false;
   int subjectLen = subject.length;
   int patternLen = pattern.length;

   while (isPat == false && iSub + patternLen - 1 < subjectLen)
   {
      if (subject [iSub] == pattern [0])
      {
         rtnIndex = iSub; // Starting at zero
         isPat = true;
         for (int iPat = 1; iPat < patternLen; iPat ++)
         {
            if (subject[iSub + iPat] != pattern[iPat])
            {
               rtnIndex = NOTFOUND;
               isPat = false;
               break;  // out of for loop
            }
         }
      }
      iSub ++;
   }
   return (rtnIndex);
}

}