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Mirrors > Home > MPE Home > Th. List > eulerpathpr | Structured version Visualization version GIF version |
Description: A graph with an Eulerian path has either zero or two vertices of odd degree. (Contributed by Mario Carneiro, 7-Apr-2015.) (Revised by AV, 26-Feb-2021.) |
Ref | Expression |
---|---|
eulerpathpr.v | ⊢ 𝑉 = (Vtx‘𝐺) |
Ref | Expression |
---|---|
eulerpathpr | ⊢ ((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) → (♯‘{𝑥 ∈ 𝑉 ∣ ¬ 2 ∥ ((VtxDeg‘𝐺)‘𝑥)}) ∈ {0, 2}) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eulerpathpr.v | . . . 4 ⊢ 𝑉 = (Vtx‘𝐺) | |
2 | eqid 2740 | . . . 4 ⊢ (iEdg‘𝐺) = (iEdg‘𝐺) | |
3 | simpl 483 | . . . 4 ⊢ ((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) → 𝐺 ∈ UPGraph) | |
4 | upgruhgr 27470 | . . . . . 6 ⊢ (𝐺 ∈ UPGraph → 𝐺 ∈ UHGraph) | |
5 | 2 | uhgrfun 27434 | . . . . . 6 ⊢ (𝐺 ∈ UHGraph → Fun (iEdg‘𝐺)) |
6 | 4, 5 | syl 17 | . . . . 5 ⊢ (𝐺 ∈ UPGraph → Fun (iEdg‘𝐺)) |
7 | 6 | adantr 481 | . . . 4 ⊢ ((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) → Fun (iEdg‘𝐺)) |
8 | simpr 485 | . . . 4 ⊢ ((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) → 𝐹(EulerPaths‘𝐺)𝑃) | |
9 | 1, 2, 3, 7, 8 | eupth2 28599 | . . 3 ⊢ ((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) → {𝑥 ∈ 𝑉 ∣ ¬ 2 ∥ ((VtxDeg‘𝐺)‘𝑥)} = if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))})) |
10 | 9 | fveq2d 6775 | . 2 ⊢ ((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) → (♯‘{𝑥 ∈ 𝑉 ∣ ¬ 2 ∥ ((VtxDeg‘𝐺)‘𝑥)}) = (♯‘if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))}))) |
11 | fveq2 6771 | . . . 4 ⊢ (∅ = if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))}) → (♯‘∅) = (♯‘if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))}))) | |
12 | 11 | eleq1d 2825 | . . 3 ⊢ (∅ = if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))}) → ((♯‘∅) ∈ {0, 2} ↔ (♯‘if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))})) ∈ {0, 2})) |
13 | fveq2 6771 | . . . 4 ⊢ ({(𝑃‘0), (𝑃‘(♯‘𝐹))} = if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))}) → (♯‘{(𝑃‘0), (𝑃‘(♯‘𝐹))}) = (♯‘if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))}))) | |
14 | 13 | eleq1d 2825 | . . 3 ⊢ ({(𝑃‘0), (𝑃‘(♯‘𝐹))} = if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))}) → ((♯‘{(𝑃‘0), (𝑃‘(♯‘𝐹))}) ∈ {0, 2} ↔ (♯‘if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))})) ∈ {0, 2})) |
15 | hash0 14080 | . . . . 5 ⊢ (♯‘∅) = 0 | |
16 | c0ex 10970 | . . . . . 6 ⊢ 0 ∈ V | |
17 | 16 | prid1 4704 | . . . . 5 ⊢ 0 ∈ {0, 2} |
18 | 15, 17 | eqeltri 2837 | . . . 4 ⊢ (♯‘∅) ∈ {0, 2} |
19 | 18 | a1i 11 | . . 3 ⊢ (((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) ∧ (𝑃‘0) = (𝑃‘(♯‘𝐹))) → (♯‘∅) ∈ {0, 2}) |
20 | simpr 485 | . . . . . 6 ⊢ (((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) ∧ ¬ (𝑃‘0) = (𝑃‘(♯‘𝐹))) → ¬ (𝑃‘0) = (𝑃‘(♯‘𝐹))) | |
21 | 20 | neqned 2952 | . . . . 5 ⊢ (((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) ∧ ¬ (𝑃‘0) = (𝑃‘(♯‘𝐹))) → (𝑃‘0) ≠ (𝑃‘(♯‘𝐹))) |
22 | fvex 6784 | . . . . . 6 ⊢ (𝑃‘0) ∈ V | |
23 | fvex 6784 | . . . . . 6 ⊢ (𝑃‘(♯‘𝐹)) ∈ V | |
24 | hashprg 14108 | . . . . . 6 ⊢ (((𝑃‘0) ∈ V ∧ (𝑃‘(♯‘𝐹)) ∈ V) → ((𝑃‘0) ≠ (𝑃‘(♯‘𝐹)) ↔ (♯‘{(𝑃‘0), (𝑃‘(♯‘𝐹))}) = 2)) | |
25 | 22, 23, 24 | mp2an 689 | . . . . 5 ⊢ ((𝑃‘0) ≠ (𝑃‘(♯‘𝐹)) ↔ (♯‘{(𝑃‘0), (𝑃‘(♯‘𝐹))}) = 2) |
26 | 21, 25 | sylib 217 | . . . 4 ⊢ (((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) ∧ ¬ (𝑃‘0) = (𝑃‘(♯‘𝐹))) → (♯‘{(𝑃‘0), (𝑃‘(♯‘𝐹))}) = 2) |
27 | 2ex 12050 | . . . . 5 ⊢ 2 ∈ V | |
28 | 27 | prid2 4705 | . . . 4 ⊢ 2 ∈ {0, 2} |
29 | 26, 28 | eqeltrdi 2849 | . . 3 ⊢ (((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) ∧ ¬ (𝑃‘0) = (𝑃‘(♯‘𝐹))) → (♯‘{(𝑃‘0), (𝑃‘(♯‘𝐹))}) ∈ {0, 2}) |
30 | 12, 14, 19, 29 | ifbothda 4503 | . 2 ⊢ ((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) → (♯‘if((𝑃‘0) = (𝑃‘(♯‘𝐹)), ∅, {(𝑃‘0), (𝑃‘(♯‘𝐹))})) ∈ {0, 2}) |
31 | 10, 30 | eqeltrd 2841 | 1 ⊢ ((𝐺 ∈ UPGraph ∧ 𝐹(EulerPaths‘𝐺)𝑃) → (♯‘{𝑥 ∈ 𝑉 ∣ ¬ 2 ∥ ((VtxDeg‘𝐺)‘𝑥)}) ∈ {0, 2}) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 ↔ wb 205 ∧ wa 396 = wceq 1542 ∈ wcel 2110 ≠ wne 2945 {crab 3070 Vcvv 3431 ∅c0 4262 ifcif 4465 {cpr 4569 class class class wbr 5079 Fun wfun 6426 ‘cfv 6432 0cc0 10872 2c2 12028 ♯chash 14042 ∥ cdvds 15961 Vtxcvtx 27364 iEdgciedg 27365 UHGraphcuhgr 27424 UPGraphcupgr 27448 VtxDegcvtxdg 27830 EulerPathsceupth 28557 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1802 ax-4 1816 ax-5 1917 ax-6 1975 ax-7 2015 ax-8 2112 ax-9 2120 ax-10 2141 ax-11 2158 ax-12 2175 ax-ext 2711 ax-rep 5214 ax-sep 5227 ax-nul 5234 ax-pow 5292 ax-pr 5356 ax-un 7582 ax-cnex 10928 ax-resscn 10929 ax-1cn 10930 ax-icn 10931 ax-addcl 10932 ax-addrcl 10933 ax-mulcl 10934 ax-mulrcl 10935 ax-mulcom 10936 ax-addass 10937 ax-mulass 10938 ax-distr 10939 ax-i2m1 10940 ax-1ne0 10941 ax-1rid 10942 ax-rnegex 10943 ax-rrecex 10944 ax-cnre 10945 ax-pre-lttri 10946 ax-pre-lttrn 10947 ax-pre-ltadd 10948 ax-pre-mulgt0 10949 ax-pre-sup 10950 |
This theorem depends on definitions: df-bi 206 df-an 397 df-or 845 df-ifp 1061 df-3or 1087 df-3an 1088 df-tru 1545 df-fal 1555 df-ex 1787 df-nf 1791 df-sb 2072 df-mo 2542 df-eu 2571 df-clab 2718 df-cleq 2732 df-clel 2818 df-nfc 2891 df-ne 2946 df-nel 3052 df-ral 3071 df-rex 3072 df-reu 3073 df-rmo 3074 df-rab 3075 df-v 3433 df-sbc 3721 df-csb 3838 df-dif 3895 df-un 3897 df-in 3899 df-ss 3909 df-pss 3911 df-nul 4263 df-if 4466 df-pw 4541 df-sn 4568 df-pr 4570 df-op 4574 df-uni 4846 df-int 4886 df-iun 4932 df-br 5080 df-opab 5142 df-mpt 5163 df-tr 5197 df-id 5490 df-eprel 5496 df-po 5504 df-so 5505 df-fr 5545 df-we 5547 df-xp 5596 df-rel 5597 df-cnv 5598 df-co 5599 df-dm 5600 df-rn 5601 df-res 5602 df-ima 5603 df-pred 6201 df-ord 6268 df-on 6269 df-lim 6270 df-suc 6271 df-iota 6390 df-fun 6434 df-fn 6435 df-f 6436 df-f1 6437 df-fo 6438 df-f1o 6439 df-fv 6440 df-riota 7228 df-ov 7274 df-oprab 7275 df-mpo 7276 df-om 7707 df-1st 7824 df-2nd 7825 df-frecs 8088 df-wrecs 8119 df-recs 8193 df-rdg 8232 df-1o 8288 df-2o 8289 df-oadd 8292 df-er 8481 df-map 8600 df-pm 8601 df-en 8717 df-dom 8718 df-sdom 8719 df-fin 8720 df-sup 9179 df-inf 9180 df-dju 9660 df-card 9698 df-pnf 11012 df-mnf 11013 df-xr 11014 df-ltxr 11015 df-le 11016 df-sub 11207 df-neg 11208 df-div 11633 df-nn 11974 df-2 12036 df-3 12037 df-n0 12234 df-xnn0 12306 df-z 12320 df-uz 12582 df-rp 12730 df-xadd 12848 df-fz 13239 df-fzo 13382 df-seq 13720 df-exp 13781 df-hash 14043 df-word 14216 df-cj 14808 df-re 14809 df-im 14810 df-sqrt 14944 df-abs 14945 df-dvds 15962 df-vtx 27366 df-iedg 27367 df-edg 27416 df-uhgr 27426 df-ushgr 27427 df-upgr 27450 df-uspgr 27518 df-vtxdg 27831 df-wlks 27964 df-trls 28057 df-eupth 28558 |
This theorem is referenced by: eulerpath 28601 |
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