Undergraduate
Engineering

The pumping lemma

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Merry 🍒

Merry 🍒

Proof idea the pumping lemma from Com Sci senior yr

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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