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Metamath Proof Explorer

Theorem spthdep

Description: A simple path (at least of length 1) has different start and end points (in an undirected graph). (Contributed by AV, 31-Jan-2021) (Proof shortened by AV, 30-Oct-2021)

Ref Expression
Assertion spthdep ( ( 𝐹 ( SPaths ‘ 𝐺 ) 𝑃 ∧ ( ♯ ‘ 𝐹 ) ≠ 0 ) → ( 𝑃 ‘ 0 ) ≠ ( 𝑃 ‘ ( ♯ ‘ 𝐹 ) ) )

Proof

Step Hyp Ref Expression
1 isspth ⊢ ( 𝐹 ( SPaths ‘ 𝐺 ) 𝑃 ↔ ( 𝐹 ( Trails ‘ 𝐺 ) 𝑃 ∧ Fun ◡ 𝑃 ) )
2 trliswlk ⊢ ( 𝐹 ( Trails ‘ 𝐺 ) 𝑃 → 𝐹 ( Walks ‘ 𝐺 ) 𝑃 )
3 eqid ⊢ ( Vtx ‘ 𝐺 ) = ( Vtx ‘ 𝐺 )
4 3 wlkp ⊢ ( 𝐹 ( Walks ‘ 𝐺 ) 𝑃 → 𝑃 : ( 0 ... ( ♯ ‘ 𝐹 ) ) ⟶ ( Vtx ‘ 𝐺 ) )
5 2 4 syl ⊢ ( 𝐹 ( Trails ‘ 𝐺 ) 𝑃 → 𝑃 : ( 0 ... ( ♯ ‘ 𝐹 ) ) ⟶ ( Vtx ‘ 𝐺 ) )
6 5 anim1i ⊢ ( ( 𝐹 ( Trails ‘ 𝐺 ) 𝑃 ∧ Fun ◡ 𝑃 ) → ( 𝑃 : ( 0 ... ( ♯ ‘ 𝐹 ) ) ⟶ ( Vtx ‘ 𝐺 ) ∧ Fun ◡ 𝑃 ) )
7 df-f1 ⊢ ( 𝑃 : ( 0 ... ( ♯ ‘ 𝐹 ) ) –1-1→ ( Vtx ‘ 𝐺 ) ↔ ( 𝑃 : ( 0 ... ( ♯ ‘ 𝐹 ) ) ⟶ ( Vtx ‘ 𝐺 ) ∧ Fun ◡ 𝑃 ) )
8 6 7 sylibr ⊢ ( ( 𝐹 ( Trails ‘ 𝐺 ) 𝑃 ∧ Fun ◡ 𝑃 ) → 𝑃 : ( 0 ... ( ♯ ‘ 𝐹 ) ) –1-1→ ( Vtx ‘ 𝐺 ) )
9 wlkcl ⊢ ( 𝐹 ( Walks ‘ 𝐺 ) 𝑃 → ( ♯ ‘ 𝐹 ) ∈ ℕ0 )
10 nn0fz0 ⊢ ( ( ♯ ‘ 𝐹 ) ∈ ℕ0 ↔ ( ♯ ‘ 𝐹 ) ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) )
11 10 biimpi ⊢ ( ( ♯ ‘ 𝐹 ) ∈ ℕ0 → ( ♯ ‘ 𝐹 ) ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) )
12 0elfz ⊢ ( ( ♯ ‘ 𝐹 ) ∈ ℕ0 → 0 ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) )
13 11 12 jca ⊢ ( ( ♯ ‘ 𝐹 ) ∈ ℕ0 → ( ( ♯ ‘ 𝐹 ) ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ∧ 0 ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ) )
14 2 9 13 3syl ⊢ ( 𝐹 ( Trails ‘ 𝐺 ) 𝑃 → ( ( ♯ ‘ 𝐹 ) ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ∧ 0 ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ) )
15 14 adantr ⊢ ( ( 𝐹 ( Trails ‘ 𝐺 ) 𝑃 ∧ Fun ◡ 𝑃 ) → ( ( ♯ ‘ 𝐹 ) ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ∧ 0 ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ) )
16 8 15 jca ⊢ ( ( 𝐹 ( Trails ‘ 𝐺 ) 𝑃 ∧ Fun ◡ 𝑃 ) → ( 𝑃 : ( 0 ... ( ♯ ‘ 𝐹 ) ) –1-1→ ( Vtx ‘ 𝐺 ) ∧ ( ( ♯ ‘ 𝐹 ) ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ∧ 0 ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ) ) )
17 eqcom ⊢ ( ( 𝑃 ‘ 0 ) = ( 𝑃 ‘ ( ♯ ‘ 𝐹 ) ) ↔ ( 𝑃 ‘ ( ♯ ‘ 𝐹 ) ) = ( 𝑃 ‘ 0 ) )
18 f1veqaeq ⊢ ( ( 𝑃 : ( 0 ... ( ♯ ‘ 𝐹 ) ) –1-1→ ( Vtx ‘ 𝐺 ) ∧ ( ( ♯ ‘ 𝐹 ) ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ∧ 0 ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ) ) → ( ( 𝑃 ‘ ( ♯ ‘ 𝐹 ) ) = ( 𝑃 ‘ 0 ) → ( ♯ ‘ 𝐹 ) = 0 ) )
19 17 18 biimtrid ⊢ ( ( 𝑃 : ( 0 ... ( ♯ ‘ 𝐹 ) ) –1-1→ ( Vtx ‘ 𝐺 ) ∧ ( ( ♯ ‘ 𝐹 ) ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ∧ 0 ∈ ( 0 ... ( ♯ ‘ 𝐹 ) ) ) ) → ( ( 𝑃 ‘ 0 ) = ( 𝑃 ‘ ( ♯ ‘ 𝐹 ) ) → ( ♯ ‘ 𝐹 ) = 0 ) )
20 16 19 syl ⊢ ( ( 𝐹 ( Trails ‘ 𝐺 ) 𝑃 ∧ Fun ◡ 𝑃 ) → ( ( 𝑃 ‘ 0 ) = ( 𝑃 ‘ ( ♯ ‘ 𝐹 ) ) → ( ♯ ‘ 𝐹 ) = 0 ) )
21 20 necon3d ⊢ ( ( 𝐹 ( Trails ‘ 𝐺 ) 𝑃 ∧ Fun ◡ 𝑃 ) → ( ( ♯ ‘ 𝐹 ) ≠ 0 → ( 𝑃 ‘ 0 ) ≠ ( 𝑃 ‘ ( ♯ ‘ 𝐹 ) ) ) )
22 1 21 sylbi ⊢ ( 𝐹 ( SPaths ‘ 𝐺 ) 𝑃 → ( ( ♯ ‘ 𝐹 ) ≠ 0 → ( 𝑃 ‘ 0 ) ≠ ( 𝑃 ‘ ( ♯ ‘ 𝐹 ) ) ) )
23 22 imp ⊢ ( ( 𝐹 ( SPaths ‘ 𝐺 ) 𝑃 ∧ ( ♯ ‘ 𝐹 ) ≠ 0 ) → ( 𝑃 ‘ 0 ) ≠ ( 𝑃 ‘ ( ♯ ‘ 𝐹 ) ) )