Code Golf: Finite-state machine!

Python 2.7+, 201 192 187 181 179 175 171 chars

PS. After the problem was relaxed (no need to output state line on empty input), here is new code that’s notably shorter. If you are on version <2.7, there is no dict comprehension, so instead of {c+o:s for o,c,s in i[1:-1]} try dict((c+o,s)for o,c,s in i[1:-1]) for the price of +5.

import sys
i=map(str.split,sys.stdin)
s=i[0][0]
for c in''.join(i[-1]):
    if s:o=s;s={c+o:s for o,c,s in i[1:-1]}.get(c+s,());print o,c,'->',s
print'ARCECJEEPCTT'[s>'Z'::2]

And its test output:

# for empty input
ACCEPT

# for input '1001010'
S1 1  ->  S1
S1 0  ->  s2
s2 0  ->  S1
S1 1  ->  S1
S1 0  ->  s2
s2 1  ->  s2
s2 0  ->  S1
ACCEPT

# for input '101'
S1 1  ->  S1
S1 0  ->  s2
s2 1  ->  s2
REJECT

# for input '10X'
S1 1  ->  S1
S1 0  ->  s2
s2 X  ->  ()
REJECT

# for input 'X10'
S1 X  ->  ()
REJECT

Previous entry (len 201):

import sys
i=list(sys.stdin)
s=i[0].split()[0]
t={}
for r in i[1:-1]:a,b,c=r.split();t[a,b]=c
try:
    for c in i[-1]:print s,c.strip(),;s=t[s,c];print' ->',s
except:print('ACCEPT','REJECT')[s>'Z'or' '<c]

I want to apologize before someone slaps me for it: the code behavior is slightly different from the original spec – per question-comments discussion. This is my illustration for the discussion.

PS. while i like the resolution ACCEPT/REJECT on the same line with the final state, it can me moved to solitude (e.g. imagine results are to be parsed by stupid script that only cares about last line being accept or reject) by adding '\n'+ (5 chars) to the last print for the price of +5 chars.

Example output:

# for empty input
S1  ACCEPT

# for input '1001010'
S1 1  -> S1
S1 0  -> s2
s2 0  -> S1
S1 1  -> S1
S1 0  -> s2
s2 1  -> s2
s2 0  -> S1
S1  ACCEPT

# for input '101'
S1 1  -> S1
S1 0  -> s2
s2 1  -> s2
s2  REJECT

# for input '10X'
S1 1  -> S1
S1 0  -> s2
s2 X REJECT

# for input 'X10'
S1 X REJECT