Faces from a mesh: Difference between revisions

=={{header|Phix}}==

<lang Phix>function perequiv(sequence a, b)

-- Works by aligning and rotating in one step, so theoretically much faster on massive sets.

bool res = (length(a)==length(b))

if res and length(a)>0 then

integer k = find(a[1],b)

if k=0 then

res = false

else

-- align with a (ie make b[1]==a[1], by

-- rotating b k places in one operation)

b = b[k..$]&b[1..k-1]

if a!=b then

-- eg {8,3,4,5} <=> {8,5,4,3}, ie

-- rotate *and* keep in alignment.

b[2..$] = reverse(b[2..$])

res = (a==b)

end if

end if

end if

-- return res

return {"false","true"}[res+1]

end function

function edge2peri(sequence edges)

sequence was = edges, res = {}

string error = ""

integer lnk

if length(edges)<2 then

error = "too short"

else

-- edges = sort(edges) -- (see note below)

res = edges[1]

edges = edges[2..$]

lnk = res[2]

while length(edges) and error="" do

bool found = false

for i=1 to length(edges) do

integer k = find(lnk,edges[i])

if k then

lnk = edges[i][3-k]

edges[i..i] = {}

if edges={} then

if lnk!=res[1] then error = "oh dear" end if

else

if find(lnk,res) then error = "oops" end if

res &= lnk

end if

found = true

exit

end if

end for

if not found then error = "bad link" exit end if

end while

end if

if length(error) then res = {error,res,lnk,edges,was} end if

return res

end function

constant ptests = {{{8, 1, 3}, {1, 3, 8}},

{{18, 8, 14, 10, 12, 17, 19}, {8, 14, 10, 12, 17, 19, 18}},

-- (check our results below against Go etc)

{{1,11,7},{1,7,11}},

{{11,23,17,1},{1,11,23,17}}}

for i=1 to length(ptests) do

sequence {p,q} = ptests[i]

printf(1,"%v equivalent to %v: %s\n",{p,q,perequiv(p,q)})

end for

constant etests = {{{1, 11}, {7, 11}, {1, 7}},

{{11, 23}, {1, 17}, {17, 23}, {1, 11}},

{{8, 14}, {17, 19}, {10, 12}, {10, 14}, {12, 17}, {8, 18}, {18, 19}},

{{1, 3}, {9, 11}, {3, 11}, {1, 11}}}

for i=1 to length(etests) do

printf(1,"%v\n",{edge2peri(etests[i])})

end for</lang>

{{out}}

(second part matches Julia/Perl: un-comment that sort above to match Go/Python/zkl)

<pre>

{8,1,3} equivalent to {1,3,8}: true

{18,8,14,10,12,17,19} equivalent to {8,14,10,12,17,19,18}: true

{1,11,7} equivalent to {1,7,11}: true

{11,23,17,1} equivalent to {1,11,23,17}: true

{1,11,7}

{11,23,17,1}

{8,14,10,12,17,19,18}

{"bad link",{1,3,11,9},9,{{1,11}},{{1,3},{9,11},{3,11},{1,11}}}

</pre>