Undergraduate
Engineering
The pumping lemma
7
203
0
Proof idea the pumping lemma from Com Sci senior yr
ノートテキスト
ページ1:
PROOF IDEA (W) The pumping lemma If A is a regular language, then there is a number of P,called length, value if S is any string of length at lost P,then it is possible to divide S into three pieces,say S= xyz, thus satisfying the following properties. iter ①For each izo, xy'z EA (reprotion of y are close possible) Cy must be non-empty) 2 lyl > 0 ③1 xy | ≤ p (xy 1 ≤ p (xy must be tateen main in the first P symbols of 5) Proof idea: . . Assume is regular.Let M be a DFA such as that L(M) = A. We then assigned P to be the number of states that M has. Lets be a string in A and ISI >= P. Let n denote the length of S, So n >= P. S = 5₁ 52 n symbol M Note that when M processing S, M move throvth n state, In other arounds sequense of state that M move through is of length n+1 Note that n+1 P+1 > P => 4+1 > P It implies that is a repeat state 19 %2 on r 2000 gr n
ページ2:
NOTE: RE R = OLDU 1) * ; L(R) = A => A is regular q 3 0,1 Tuesday, 20 Feb, 2025 4. 1 0 0₂ q₂ DFA M St. L(M) = A S = O O O E A Consider s = Consider the sequense Y X Z X 0 9. . D D 0 9 911 0 912 Z 0 Proof of lemma: ♥Assume that A su regular lu' m = [Q, 1, 8, & start, F] เป็น DFA ใน L(M) = A ♥Consider a String Car โดย qu s = 5₁ 5 ₂... Sn Then, Consider 651 m เราทำ Pumping ในรูป P = IQ) = 151 = n ≥P SEA และ S Sequense 216 State Mau r=r₁₂r₁₂ Observe that n+1 ≥ P + 1 > P ; n + 1 > P 0 at least are responted state in sequense r. 9 start ↑ accept ง Z ↑ r 0 ๆ ง 7 2 r 87 r r r ง ๆ 10 ) 。 。 。 ง n r = r₁₁₁ : mรแบ่ง S = xyz n + 1 start S t is a section that bake's M from 9 start + = 9 rn qi Y Z 99 99 99 q; back to qi 97 qi to accept
ページ3:
qs (q as follow! qi - The division satisfies each of the three condition" ①Vi, xy'z E A This is clearly true. ②lyl > 0 This is due to two different 2 (3) ③Ixyl ≤ p This first P+1 state in the sequense P V must have a repeation. Provine Non-regularlority. J J 5 • To prove toๆ จัง งัด แข็งเราจะทำการแสดง Con tradition) ภายหลัง ♡ 25 Pumping lemma leth P. d 9 หา String ใน J & B โดย ขนาด 1ST - P และ Show that such string s cannot be pumping Considerirs all possible. B. 9 กา เกา ( above, เมื่อเรามี Contradiction และ B ไม่เป็น regular ถ้า
ページ4:
n
E. S. 1 B = 0" 1" n≥
{ { o^ ₁" | n ≥ 0 } We show that B is not regular.
Sol - Assume that
- Let
B
is
regular to obtain a contracdition
P
be the pumping Tenth.
=
- Chose a string E - OF; PEB, and so 1s1 = 2p>p
-
- Chose a divition s =
xyz
K>○
• To satifly ①, we must take y as y=ok, k>0
จ
and
x =
and Z
ด
• The division already satifies C②CL
0 0 ... 0 0
11
11
P ตัว
Poła
The division cannot satify ①
xyz
=
=
l
of (ok); OP- (k+1) 1
= 0.0
= 0
0
P
-
ik
K tik
1+(k+1)
P
1
P + (i-1) k p
1
Note OP+ (i-1)k, P & B, when i>o
P
P
1
1.06
also OP+ B,
P+ (i-1)k, P & B also when it
0
=
น
ページ5:
ES2 C = {wlw has an equre number of Os and 1s}
Note: Since BCC, I's not regular, but we wish to show a
string in C that cannot we purpond.
P/2
9
1
P/2
Consider: S 0
0 P/2
=
and ISI
=
2P>P
1
1
P/2
E C
② 5´ = (01) P = 010101... 01 € C
E
Pump ได๋
2P>P
and 151
ap
=
P
=
0
1 P o E C
1 1
2P+2
and Is1 = 2P+2>P
Is'I
Pump
P/2
P/2
1
Sol
P/2
1) S
0
1
P/2
0
า
Z
X
y
E
P/2
0 1
P/2
P/2
0
1
P/2
S= xyz where x = 2₁ y
E C
=0%2
ง
E C and ISI = 2P>P
P/2 P/2
Z = 0
1
sati fies,, and so we can pump it
010101 01 Ed and 151 = 2P>P
2)5
2) 5´ = (01) P = 010101.
ap
x
y
Z
01 01 01. 01 =
£ 0 1 01
01
0 1 0 1 -
01
P
P
5=
xyz
where
x = Z
2 y
=
(01 )
Satifie 0,
ๆ
P/2
72-(01)8/2
=
and so we pump it
ページ6:
P 3 ) 5 " = 0³ 1 1 ³ 0 € C and 1s = 1 = 2p + 2 >p 2P+2 P E S" = 0³ 1 1 0 E C 47 00... 00 111 1 P P S² = xyz x = 0l where Y = 0x P = (k + l) P Z = 0 11 OK >0 #0 09 satifies ③, 1", but con not ⑥ (3 (2) bc Vi, xy'z of cok = P op -(k+1); 10 =0P+ (i-1) k 11 P0 when i> the number of Os > the number of 15 C. resulting string, which isn't in C
ページ7:
E. S 3
D = { 0 ² 1 j ; i >; }; Show that D is not regular.
KP-k
Sol 1 S = ok 1
P-ķ
k> P/2
E D 151
9
00...@ 11 ... 11
P
K- (P-K) = 2
P
P-k
≥ P
S' = D³ 01³ & D, Isl = 2p+22 P
ง
00. 00 11 ... 11
regular
language
M
P
P
Pumping
=> 0² ₁P & D
1
#D
•Universe of all language
non regular
n
[B,C,D, JB = {o" "In 20}
1
*lem da Calculust
Computional Pome ; Finite Automata < Push down Automata<
Turing Machine ( Regular Expression
< Context - free Grammar <Becusive language
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