File size: 10,982 Bytes
5d5048e
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
import OAI.Combinatorics.ListHadwiger.Recursion

namespace OAI

namespace LinearListHadwiger.Recursion
open SimpleGraph Finset
attribute [local instance] Classical.propDecidable
variable {V I : Type} [DecidableEq V] [Fintype I] {G : SimpleGraph V}

theorem reroute_selected (J : Set V) {a b : ℕ} (hJ : WovenOn G J a b)
    (u : Fin a → V) (hu : Function.Injective u) (huJ : ∀ j, u j∈J)
    (keep : Fin a → Prop)
    (x y : I → V) (P : ∀ i, G.Path (x i) (y i))
    (hcard : Fintype.card I ≤ b)
    (hPP : ∀ i j, i≠j → Disjoint {v | v∈(P i).val.support} {v | v∈(P j).val.support})
    (hroot : ∀ i j, keep j → u j∈(P i).val.support → u j=x i) :
    ∃ M : RootedCliqueModel G u, (∀ j, M.branch j⊆J) ∧
    ∃ Q : ∀ i, G.Path (x i) (y i),
      (∀ i j, i≠j → Disjoint {v | v∈(Q i).val.support} {v | v∈(Q j).val.support}) ∧
      (∀ i v, v∈(Q i).val.support → v∉J → v∈(P i).val.support) ∧
      (∀ i j v, keep j → v∈(Q i).val.support → v∈M.branch j → v=x i ∧ v=u j) := by
  classical
  let e : Fin (Fintype.card I) ≃ I := (Fintype.equivFin I).symm
  obtain ⟨M,hMJ,Q,hQQ,_,hQP,hQM⟩ := reroute_woven_district G J hJ u hu huJ
    (x ∘ e) (y ∘ e) (fun i => P (e i)) hcard
    (fun i j hij => hPP _ _ (fun h => hij (e.injective h)))
  let Q' : ∀ i, G.Path (x i) (y i) := fun i =>
    ⟨(Q (e.symm i)).val.copy (congrArg x (e.apply_symm_apply i))
      (congrArg y (e.apply_symm_apply i)),by simp⟩
  have hsup (i : I) (v : V) : v∈(Q' i).val.support ↔ v∈(Q (e.symm i)).val.support := by
    simp [Q']
  refine ⟨M,hMJ,Q',?_,?_,?_⟩
  · intro i j hij
    apply Set.disjoint_left.mpr
    intro v hv hw
    exact Set.disjoint_left.mp (hQQ _ _ (fun h => hij (e.symm.injective h)))
      ((hsup i v).mp hv) ((hsup j v).mp hw)
  · intro i v hv hvJ
    have he := congrArg (fun j => (P j).val.support) (e.apply_symm_apply i)
    exact he ▸ hQP _ v ((hsup i v).mp hv) hvJ
  · intro i j v hjkeep hv hvm
    obtain ⟨⟨j',rfl⟩,D,hD⟩ := hQM _ j v ((hsup i v).mp hv) hvm
    have hj : j'=j := by
      by_contra hne
      exact Set.disjoint_left.mp (M.disjoint j' j hne) (M.root_mem j') hvm
    have horig : u j'∈(P i).val.support := by
      have he := congrArg (fun j => (P j).val.support) (e.apply_symm_apply i)
      rw [←he]
      rcases hD with hd | hd
      · exact hd.symm ▸ D.entry_on
      · exact hd.symm ▸ D.exit_on
    exact ⟨hroot i j' (hj ▸ hjkeep) horig,congrArg u hj⟩

omit [DecidableEq V] [Fintype I] in
lemma source_only (x y : I → V) (P : ∀ i, G.Path (x i) (y i))
    (hPP : ∀ i j, i≠j → Disjoint {v | v∈(P i).val.support} {v | v∈(P j).val.support})
    (i j : I) (h : x j∈(P i).val.support) : x j=x i := by
  by_cases he : i=j
  · exact he ▸ rfl
  · exact (Set.disjoint_left.mp (hPP i j he) h (P j).val.start_mem_support).elim

omit [DecidableEq V] [Fintype I] in

lemma rooted_of_occurrences {O : Type} (G : SimpleGraph V) (r : I → V)
    (hr : Function.Injective r) (label : O → I) (B : O → Set V)
    (hB : ∀ o, (G.induce (B o)).Connected)
    (hBB : ∀ o p, label o≠label p → Disjoint (B o) (B p))
    (hroot : ∀ o i, r i∉B o)
    (hattach : ∀ o, ∃ v∈B o, G.Adj v (r (label o)))
    (hpairs : ∀ i j, i≠j → ∃ o p, label o=i ∧ label p=j ∧
      ∃ v∈B o, ∃ w∈B p, G.Adj v w) :
    ∃ M : RootedCliqueModel G r,
      ∀ i, M.branch i={r i}∪{v | ∃ o, label o=i ∧ v∈B o} := by
  let C (i : I) := {r i}∪{v | ∃ o, label o=i ∧ v∈B o}
  have hc (i) : (G.induce (C i)).Connected := by
    have hsingleton : (G.induce ({r i}:Set V)).Connected := by
      have : Nonempty ({r i}:Set V) := ⟨⟨r i,rfl⟩⟩
      exact Connected.of_subsingleton
    have h := Assembly.connected_glue G {r i}
      (fun o : {o // label o=i} => B o.val) hsingleton (fun o => hB o.val) (fun o => by
        obtain ⟨v,hv,he⟩ := hattach o.val
        exact ⟨v,hv,r i,rfl,by simpa only [o.property] using he⟩)
    have he : C i={r i}∪{v | ∃ o : {o // label o=i},v∈B o.val} := by
      ext v
      simp only [C,Set.mem_union,Set.mem_ofPred_eq,Subtype.exists,exists_prop]
    exact he ▸ h
  refine ⟨⟨C,hc,?_,?_,fun _ => Or.inl rfl⟩,fun _ => rfl⟩
  · intro i j hij
    apply Set.disjoint_left.mpr
    intro v hi hj
    rcases hi with hi | ⟨o,ho,hi⟩ <;> rcases hj with hj | ⟨p,hp,hj⟩
    · exact hij (hr (hi.symm.trans hj))
    · exact hroot p i (hi ▸ hj)
    · exact hroot o j (hj ▸ hi)
    · exact Set.disjoint_left.mp (hBB o p (by simpa only [ho,hp] using hij)) hi hj
  · intro i j hij
    obtain ⟨o,p,ho,hp,v,hv,w,hw,he⟩ := hpairs i j hij
    exact ⟨v,Or.inr ⟨o,ho,hv⟩,w,Or.inr ⟨p,hp,hw⟩,he⟩

theorem reroute_disjoint_districts {D : Type} [Fintype D]
    (J : D → Set V) {a b : ℕ} (hJ : ∀ d, WovenOn G (J d) a b)
    (hJJ : ∀ d e, d≠e → Disjoint (J d) (J e))
    (u : D → Fin a → V) (hu : ∀ d, Function.Injective (u d)) (huJ : ∀ d j, u d j∈J d)
    (x y : I → V) (P : ∀ i, G.Path (x i) (y i))
    (hcard : Fintype.card I≤b)
    (hPP : ∀ i j, i≠j → Disjoint {v | v∈(P i).val.support} {v | v∈(P j).val.support}) :
    ∃ M : ∀ d, RootedCliqueModel G (u d), (∀ d j, (M d).branch j⊆J d) ∧
    ∃ Q : ∀ i, G.Path (x i) (y i),
      (∀ i j, i≠j → Disjoint {v | v∈(Q i).val.support} {v | v∈(Q j).val.support}) ∧
      (∀ i v, v∈(Q i).val.support → (∀ d, v∉J d) → v∈(P i).val.support) ∧
      (∀ d i j v, (∃ k, x k=u d j) → v∈(Q i).val.support →
        v∈(M d).branch j → v=x i ∧ v=u d j) := by
  classical
  have step (S : Finset D) :
      ∃ M : ∀ d∈S, RootedCliqueModel G (u d), (∀ d hd j, (M d hd).branch j⊆J d) ∧
      ∃ Q : ∀ i, G.Path (x i) (y i),
        (∀ i j, i≠j → Disjoint {v | v∈(Q i).val.support} {v | v∈(Q j).val.support}) ∧
        (∀ i v, v∈(Q i).val.support → (∀ d, v∉J d) → v∈(P i).val.support) ∧
        (∀ d hd i j v, (∃ k, x k=u d j) → v∈(Q i).val.support →
          v∈(M d hd).branch j → v=x i ∧ v=u d j) := by
    induction S using Finset.induction_on with
    | empty =>
      refine ⟨fun d hd => (notMem_empty d hd).elim,fun d hd => (notMem_empty d hd).elim,
        P,hPP,fun _ _ hv _ => hv,fun d hd => (notMem_empty d hd).elim⟩
    | @insert d S hd ih =>
      obtain ⟨M,hMJ,Q,hQQ,hQP,hQM⟩ := ih
      obtain ⟨N,hNJ,R,hRR,hRQ,hRN⟩ := reroute_selected (J d) (hJ d) (u d) (hu d) (huJ d)
        (fun j => ∃ i, x i=u d j) x y Q hcard hQQ (by
          intro i j hj hv
          obtain ⟨k,hk⟩ := hj
          rw [←hk] at hv
          exact hk.symm.trans (source_only x y Q hQQ i k hv))
      let M' : ∀ e∈insert d S, RootedCliqueModel G (u e) := fun e he =>
        if h : e=d then h.symm ▸ N else M e ((mem_insert.mp he).resolve_left h)
      have hnew (he : d∈insert d S) : M' d he=N := by simp [M']
      have hold (e : D) (he : e∈insert d S) (hne : e≠d) :
          M' e he=M e ((mem_insert.mp he).resolve_left hne) := by simp [M',hne]
      refine ⟨M',?_,R,hRR,?_,?_⟩
      · intro e he j
        by_cases h : e=d
        · subst e
          rw [hnew he]
          exact hNJ j
        · rw [hold e he h]
          exact hMJ e _ j
      · intro i v hv hvJ
        exact hQP i v (hRQ i v hv (hvJ d)) hvJ
      · intro e he i j v hj hv hvm
        by_cases h : e=d
        · subst e
          rw [hnew he] at hvm
          exact hRN i j v hj hv hvm
        · rw [hold e he h] at hvm
          have hvJ : v∉J d := fun hvd =>
            Set.disjoint_left.mp (hJJ e d h) (hMJ e _ j hvm) hvd
          exact hQM e _ i j v hj (hRQ i v hv hvJ) hvm
  obtain ⟨M,hMJ,Q,hQQ,hQP,hQM⟩ := step univ
  exact ⟨fun d => M d (mem_univ d),fun d j => hMJ d _ j,Q,hQQ,hQP,
    fun d => hQM d (mem_univ d)⟩

lemma paired_paths_on [Fintype V] [DecidableEq I]
    (G : SimpleGraph V) (S : Finset V) (z : I × Bool → V)
    (hz : Function.Injective z) (hzS : ∀ o, z o∈S)
    (hI : 1≤Fintype.card I)
    (hc : KConnectedOn G S (65536*(2*Fintype.card I))) :
    ∃ P : ∀ i, G.Path (z (i,false)) (z (i,true)),
      (∀ i v, v∈(P i).val.support → v∈S) ∧
      ∀ i j, i≠j → Disjoint {v | v∈(P i).val.support} {v | v∈(P j).val.support} := by
  have hp : 1≤Fintype.card (I × Bool) := by simp only [Fintype.card_prod,Fintype.card_bool]; omega
  have hc' : KConnectedOn G S (65536*Fintype.card (I×Bool)) := by
    simpa only [Fintype.card_prod,Fintype.card_bool,Nat.mul_comm (Fintype.card I) 2] using hc
  obtain ⟨C,hC,hCC,hCS,hzC⟩ := Stage.grouped_ends G S z hz hzS Prod.fst
    (fun i => ⟨(i,false),rfl⟩) hp hc'
  have hex (i : I) : ∃ P : G.Path (z (i,false)) (z (i,true)), ∀ v∈P.val.support, v∈C i :=
    Assembly.path_in_connected (hC i) (hzC (i,false)) (hzC (i,true))
  choose P hP using hex
  refine ⟨P,fun i v hv => hCS i (hP i v hv),?_⟩
  intro i j hij
  exact Set.disjoint_left.mpr (fun v hi hj => Set.disjoint_left.mp (hCC i j hij) (hP i v hi) (hP j v hj))

omit [DecidableEq V] [Fintype I] in

lemma rooted_from_bag_routes {O : Type} (G : SimpleGraph V)
    (r : I → V) (hr : Function.Injective r) (label : O → I)
    (x y : O → V) (hx : Function.Injective x)
    (C : O → Set V) (P : ∀ o, G.Path (x o) (y o))
    (hC : ∀ o, (G.induce (C o)).Connected) (hCx : ∀ o, x o∈C o)
    (hCC : ∀ o p, o≠p → Disjoint (C o) (C p))
    (hPP : ∀ o p, o≠p → Disjoint {v | v∈(P o).val.support} {v | v∈(P p).val.support})
    (hPC : ∀ o p v, v∈(P o).val.support → v∈C p → v=x o ∧ v=x p)
    (hRC : ∀ o i, r i∉C o)
    (hRP : ∀ o i, r i∉(P o).val.support)
    (hadj : ∀ o, G.Adj (y o) (r (label o)))
    (hpairs : ∀ i j, i≠j → ∃ o p, label o=i ∧ label p=j ∧
      ∃ v∈C o, ∃ w∈C p, G.Adj v w) :
    ∃ M : RootedCliqueModel G r, ∀ i,
      M.branch i={r i}∪{v | ∃ o, label o=i ∧ (v∈C o ∨ v∈(P o).val.support)} := by
  let B (o : O) := C o∪{v | v∈(P o).val.support}
  have hB (o) : (G.induce (B o)).Connected :=
    Stage.attached_connected C x y P hC hCx o
  have hBB (o p) (hop : label o≠label p) : Disjoint (B o) (B p) := by
    have hne : o≠p := fun h => hop (congrArg label h)
    apply Set.disjoint_left.mpr
    intro v ho hp
    rcases ho with ho|ho <;> rcases hp with hp|hp
    · exact Set.disjoint_left.mp (hCC o p hne) ho hp
    · have he := hPC p o v hp ho
      exact hne (hx (he.2.symm.trans he.1))
    · have he := hPC o p v ho hp
      exact hne (hx (he.1.symm.trans he.2))
    · exact Set.disjoint_left.mp (hPP o p hne) ho hp
  apply rooted_of_occurrences G r hr label B hB hBB
  · intro o i hi
    exact hi.elim (hRC o i) (hRP o i)
  · intro o
    exact ⟨y o,Or.inr (P o).val.end_mem_support,hadj o⟩
  · intro i j hij
    obtain ⟨o,p,ho,hp,v,hv,w,hw,he⟩ := hpairs i j hij
    exact ⟨o,p,ho,hp,v,Or.inl hv,w,Or.inl hw,he⟩

end LinearListHadwiger.Recursion

end OAI