Code Golf: Finite-state machine!

Answer 1

C# - 453 375 353 345 characters

This doesn't win (not that anyone should have expected it to), but it was fun to write anyway. I kept the leading spaces and newlines for legibility:

using System;
class P
{
  static void Main()
  {
    string c,k="";
    var t=new string[99999][];
    int p=-1,n;
    while((c=Console.ReadLine())!="")
      t[++p]=c.Split(' ');

    c=t[0][0];
    foreach(var d in t[p][0]){
      k+=c+' '+d;
      for(n=1;n'Z'?"REJECT":"ACCEPT"));
  }
}

In my last update I was able to save 22 characters by assuming a practical limit to the number of input rows (namely 99,999). In the worst case, you'd need to up that to the Int32 max of 2,147,483,647 which would add 5 chars. My machine doesn't like the idea of an array that long though...

An example of the execution:

>FSM.exe
S1 s2
S1 0 s2
S1 1 S1
s2 0 S1
s2 1 s2
1001010

S1 1 -> S1
S1 0 -> s2
s2 0 -> S1
S1 1 -> S1
S1 0 -> s2
s2 1 -> s2
s2 0 -> S1
ACCEPT