aoc2022d7.dyalog

∇out←dir lines;l;path;size;ls
 path←⊂''
 ls←⍬
 size←0
 :For l :In lines
     :If 1=⍴('\$ cd'⎕S'$1')l
         ls,←⊂(⊃{⍺,'/',⍵}/path)size
         :If '..'≢5↓l
             path,←⊂5↓l
         :Else
             path←¯1↓path
         :EndIf
         size←0
     :ElseIf 1≤⍴('^[0-9]'⎕S 0)l
         size+←⊃(//⎕VFI)l
     :EndIf
 :EndFor
 ls,←⊂(⊃{⍺,'/',⍵}/path)size
 out←ls
∇
isprefix←⊃⍷
vv←dir data
indx←(↑vv)[;1]
foo←{⊃⊃+/((⍵∘isprefix)¨indx)/(↑vv)[;2]}¨indx
z←indx {⊃⍵}⌸ foo
⍝ Part I
+/(z≤100000)/z
⍝ Part II
⌊/(z≥30000000-70000000-⊃z)/z