2016/06/28
2.5
D3
2016/06/28
Abstract•
→
•
• G | | = | | - | | + 2
• G K5 K3,3
•
2016/06/28
Outline
•
• ( )
• •
• •
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Outline
•
• ( )
• •
• •
2016/06/28
2.28
• (simple Jordan curve):
• φ: [0,1] → ℝ2 (= )
• φ(0) φ(1)
• (closed Jordan curve):
• φ(0)=φ(1) 0≤x<x'<1 φ(x)≠φ(x')
φ: [0,1] → ℝ2 (= )
2016/06/28
• (polygonal arc):
• (polygon):
2016/06/28
(connected region)
• :
• J R = ℝ2 \ J
• p,q R (= J
)
• J
• 1 (= J )
1
2016/06/28
2.29 • ψ: V(G) → ℝ2
• e = {x,y} Je ( ψ(x), ψ(y) )
• e = {x,y}
ψ {Je : e∈E(G)} G
•
(Je \ { (x), (y)}) \ { (v) : v 2 V (G)} [
[
e02E(G)\{e}
Je0
!= ;
Je\{ψ(x),ψ(y)}
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(planar graph)
• G (planar) :
G
• Φ (face) :
Φ
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• K4
• K5 ( )
• ( 24)
• ( )
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2.30
:
1. J
2. J 2
→ 2 J
3. J 1
4. J J 2
J ℝ2\J 2
2 J J
ℝ2\J 1
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2.30
:
1. J
p∈ℝ2\J, q∈J p q ℝ2\J∪{q}
(J J q )
J ℝ2\J 2
2 J J
ℝ2\J 1
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2.30
:
2. J 2
p∈ℝ2\J, q∈J →
p q 1
q
→ 2 J
J ℝ2\J 2
2 J J
ℝ2\J 1
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2.30
:
3. J 1
J ℝ2\J 2
2 J J
ℝ2\J 1
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2.30
:
4. J 2
p∈ℝ2\J α lα
lα J " " cr(p, lα) α
cr(p,lα) → gp(α) = cr(p,lα) mod 2
J ℝ2\J 2
2 J J
ℝ2\J 1p J
lα
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2.30
:
4. J 2
gp(α) = cr(p,lα) mod 2
pspt J → p∈pspt gp → gp
pspt J 1 → gps, gpt
gp 2 2
J ℝ2\J 2
2 J J
ℝ2\J 1
J ℝ2\J 2
2 J J
ℝ2\J 1
ps pt
ps pt
lα
lα
J
J
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(outer face)
•
1
•
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Outline
•
• ( )
• •
• •
2016/06/28
2.31 2-
:
1. G (∵ 2.30)
2. G
1
x x-1
G Φ 2-
2
= |E(G)| - |V(G)| + 2
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2.31 2-
:
1. G (∵ 2.30)
- G {Je}
→ 2
{Je} 2 |E(G)| = |V(G)|
G Φ 2-
2
= |E(G)| - |V(G)| + 2
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2.31 2-
:
2. G
P G'
F' F' (C )
P x,y C x,y x-y- 2 (Q1, Q2 )
Q1+P, Q2+P F' 2 → 1
P |E(P)| - (|V(P)| - |{x,y}|) = 1 = -
G Φ 2-
2
= |E(G)| - |V(G)| + 2
P Q1 Q2
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2.32
:
1. G 2- (∵ 2.31)
2.
G
= |E(G)| - |V(G)| + 2
2016/06/28
2.32
:
2.
G1, ..., Gk Fk |E(Gk)| - |V(Gk)| + 2 1
+
F = Σk Fi-1 + 1 = Σk(|E(Gi)| - |V(Gi)| + 1) + 1 = |E(G)| - (|V(G)| + k - 1) + k + 1 = |E(G)| - |V(G)| + 2
G
= |E(G)| - |V(G)| + 2
Gi x
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(girth)
• G
= 4
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2.33
:
G Φ r r = |E(G)| + |V(G)| + 2 (∵ 2.32)
G 2- 2.31 2 (= )
k kr ≤ 2|E(G)|
|E(G)| - |V(G)| + 2 ≤ 2/k |E(G)| |E(G)| ≤ (n-2) k / (k-2)
G 2- 2-
k≥3 (n-2)×3 / (3-2) = 3n-6 ( )
G n k 2-
(n-2) k / (k-2)
G n ≥ 3 3n-6
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2.34 K5, K3,3
:
2.33
K5: 10 > 3×5 - 6 = 9
K3,3: 2- 4 9 > (6-2)×4 / (4-2) = 8
K5, K3,3
K5: 5K3,3: 3 3
2016/06/28
Outline
•
• ( )
• •
• •
2016/06/28
2.35 • G,H:
• H H' V(H') = V1
∪ ... ∪ Vk H' Vi 1 G
G H
• H (1) (G-v) (2) (G-e)
(3) (G/e) G G H
H G
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•
→
• K5, K3,3
•
H G
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2.36 35 3- G G/e 3-
e
:
e
→ e = {v,w} 3-
→ G - {v,w,x} x C
C x y G/{x,y} 3-
→ G - {x,y,z} z
→ v,w v,w D
D C ( ) C
zy
x v wCD
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2.36 35 3- G G/e 3-
e
: D C ( )
C: G - {v,w,x}
D: v,w G - {x,y,z}
y d∈D → {y,d} d ∈ V(C)
D: d v,w,x,y,z
C: d x,y,z
D ⊆ C y∈V(C) y∉V(D) D ⊂ C
zy
x v wC
Dd
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2.37 33-
K5 K3,3
:
)
)
2.36 e={v,w} 3-
( ) 2-
( 2.31)
K5 K3,3
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2.37 33-
K5 K3,3
:
)
e={v,w} G/e x
G/e-x ψ(x) → C
w v y1, ..., yk
C yi-yi+1 Pi w Γ(w) ⊆ {v}∪Pi i
( ) →
w v
P2P1
P3
P4
P5
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2.37 33-
K5 K3,3
: C = ∪Pi Γ(w) ⊆ {v}∪Pi i
(1) w y1, ..., yk 3 :
K5
wv
y1y2
y3
y4y5
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2.37 33-
K5 K3,3
: C = ∪Pi Γ(w) ⊆ {v}∪Pi i
(2) w y1, ..., yk 2 :
K3,3
wv
ysyi
ytyj
w v
ys
yt yj
yi
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2.37 33-
K5 K3,3
: C = ∪Pi Γ(w) ⊆ {v}∪Pi i
(3) w Pi Pi :
K3,3
(1)~(3) w
v
yiyi+1
z2
w v
yi
yi+1 z2
z1
z1
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2.38
G 3- 5 K5 K3,3
e={v,w} G+e K5 K3,3
2 v, w
:
1.
2. x x x y, z
3. 2- x,y
a. 3- (∵ 2.37)
b. 2
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2.38
G 3- 5 K5 K3,3
e={v,w} G+e K5 K3,3
2 v, w
:
1. :
3- G-X X = {x,y}
G1 = G[V(C)∪X], G2 = G-V(C)
: v,w ∈ V(G1) e = {v,w} K5, K3,3 G+e
G1+e+f G2+f K5, K3,3 (f = {x,y})
y
xG2G1
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2.38
:
V(G1) Z1, ..., Zt
Zi K5 (t=5) K3,3 (t=6) Z
Zi ⊆ V(G1) \ X Zj ⊆ V(G2) \ X i, j
(∵x, y 2 Zk Zi, Zj → K5, K3,3 3- )
(a) Zi ⊆ V(G1) \ X Zi → G2+f K5, K3,3
(b) Zi ⊆ V(G2) \ X Zi → G1+e+f K5, K3,3
: v,w ∈ V(G1) e = {v,w} K5, K3,3 G+e
G1+e+f G2+f K5, K3,3 (f = {x,y})
y
xG2G1
f
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2.38
G 3- 5 K5 K3,3
e={v,w} G+e K5 K3,3
2 v, w
: 2. x x x y, z
(G 3- )
z G-x y z∈V(G1)
e = {y,z} G+e K5, K3,3 G1+e
G2 K5, K3,3 (f G )
G1+e y 2 G1 G2 G
: v,w ∈ V(G1) e = {v,w} K5, K3,3 G+e
G1+e+f G2+f K5, K3,3 (f = {x,y})
y
xG2G1
fz
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2.38
: 3. 2- x,y
G 2- f = {x,y} E(G)
G+f K5, K3,3 G1+f
G2+f K5, K3,3 G 2- G1, G2
x-y- f
→ G1, G2 K5, K3,3
G 3- 5 K5 K3,3
e={v,w} G+e K5 K3,3
2 v, w
: v,w ∈ V(G1) e = {v,w} K5, K3,3 G+e
G1+e+f G2+f K5, K3,3 (f = {x,y})
y
xG2G1
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2.38
G 3- 5 K5 K3,3
e={v,w} G+e K5 K3,3
2 v, w
: 3-a. 3- (∵ 2.37)
Gi 5 K5 K3,3
→ 2.37 Gi 3-
→ Gi e e OK
: v,w ∈ V(G1) e = {v,w} K5, K3,3 G+e
G1+e+f G2+f K5, K3,3 (f = {x,y})
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2.38
G 3- 5 K5 K3,3
e={v,w} G+e K5 K3,3
2 v, w
: 3-b. 2
Gi Φi f = {x,y} Fi
( 31)
zi∉{x,y} Fi e = {z1,z2} OK
G+e K5 K3,3
y
xF2F1 z2z1
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2.38
G 3- 5 K5 K3,3
e={v,w} G+e K5 K3,3
2 v, w
: zi∉{x,y} Fi e = {z1,z2} OK
G+e Z1, ..., Zt Zi K5 (t=5)
K3,3 (t=6)
(1) V(G1) \ {x,y} Zi 1
w F2 y
xF2
z2w
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2.38
G 3- 5 K5 K3,3
e={v,w} G+e K5 K3,3
2 v, w
: zi∉{x,y} Fi e = {z1,z2} OK
G+e Z1, ..., Zt Zi K5 (t=5) K3,3 (t=6)
(2) V(Gk) \ {x,y} Zi 2
Z1,Z2 ∈ V(G1) \ {x,y}, Z3,Z4 ∈ V(G2) \ {x,y} z1∉Z1, z2∉Z3,
Z1 Z3 K5
Z1 Z3 Z5, Z6 K3,3
yx
Z4
z2
Z2
Z3Z1
z1
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2.39 Kuratowski
:
)
) 2.37 2.38
3- 2.38 3-
K5, K3,3 3- 2.37
K5
K3,3
2016/06/28
Kuratowski
• ( 29)
• K5 K3,3
•
( 28(b))
• 3- 3-
K5 K3,3
2016/06/28
2.40
• Hopcroft and Tarjan [1974]
• ( )
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