%!PS

% begin included library code
% see https://codeberg.org/Firedrake/postscript-libraries/
/a2s {
    2 dict begin
    /i exch def
    i length dup string /o exch def
    1 sub 0 exch 1 exch {
        dup i 3 -1 roll get o 3 1 roll put
    } for
    o
    end
} bind def

/s2a {
    [ exch { } forall ]
} bind def

/quicksort.main { % lo hi -> (null)
    3 dict begin
    /hi exch def
    /lo exch def
    /xit false def
    lo 0 lt {
        /xit true def
    } if
    hi 0 lt {
        /xit true def
    } if
    lo hi ge {
        /xit true def
    } if
    xit not {
        /p quicksort.partition def
        lo p quicksort.main
        p 1 add hi quicksort.main
    } if
    end
} bind def

/quicksort.with_comparator { % [ a c b ] { comparator } -> [ a b c ]
    2 dict begin
    /cmp exch def
    /arr exch def
    arr length 0 gt {
        0 arr length 1 sub quicksort.main
    } if
    arr
    end
} bind def

/test.start {
    print (:) print
    /test.pass 0 def
    /test.count 0 def
} bind def

/keys { % dict -> array of dict keys
    [ exch
      {
          pop
      } forall
    ]
} bind def

/deepeq {
    2 dict begin
    /a exch def
    /b exch def
    a type b type eq {
        a type /dicttype eq {
            a length b length eq {
                <<
                    a {
                        pop
                        true
                    } forall
                    b {
                        pop
                        true
                    } forall
                >>
                true exch
                {
                    pop
                    dup a exch known {
                        dup b exch known {
                            dup a exch get exch b exch get deepeq not {
                                pop false
                            } if
                        } {
                            false
                        } ifelse
                    } {
                        false
                    } ifelse
                } forall
            } {
                false
            } ifelse
        } {
            a type dup /arraytype eq exch /stringtype eq or {
                a length b length eq {
                    true
                    0 1 a length 1 sub {
                        dup a exch get exch b exch get deepeq not {
                            pop false
                            exit
                        } if
                    } for
                } {
                    false
                } ifelse
            } {
                a b eq
            } ifelse
        } ifelse
    } {
        false
    } ifelse
    end
} bind def

/quicksort.cmp {
    2 copy
    lt {
        pop pop -1
    } {
        gt {
            1
        } {
            0
        } ifelse
    } ifelse
} bind def

/test {
    /test.count test.count 1 add def
    {
        /test.pass test.pass 1 add def
    } {
        ( ) print
        test.count (....) cvs print
        (-fail) print
    } ifelse
} bind def

/quicksort {
    { quicksort.cmp } quicksort.with_comparator
} bind def

/quicksort.partition {
    3 dict begin
    /pivot arr hi lo add 2 idiv get def
    /i lo 1 sub def
    /j hi 1 add def
    {
        {
            /i i 1 add def
            arr i get pivot cmp 0 ge {
                exit
            } if
        } loop
        {
            /j j 1 sub def
            arr j get pivot cmp 0 le {
                exit
            } if
        } loop
        i j ge {
            j
            exit
        } if
        i j quicksort.swap
    } loop
    end
} bind def

/quicksort.swap {
    2 dict begin
    /bi exch def
    /ai exch def
    arr ai get
    arr bi get
    arr exch ai exch put
    arr exch bi exch put
    end
} bind def

/test.end {
    ( ) print
    test.count 0 gt {
        (Passed ) print
        test.pass (...) cvs print
        (/) print
        test.count (...) cvs print
        ( \() print
        test.pass 100 mul test.count idiv (...) cvs print
        (%\)) print
        (\r\n) print
    } if
} bind def


% end included library code

/counterify {
    2 dict begin
    /c 0 dict def
    {
        /n exch def
        c n known {
            c n 2 copy get 1 add put
        } {
            c n 1 put
        } ifelse
    } forall
    c
    end
} bind def

/commoncharacters {
    0 dict begin
    /mc 0 dict def
    /first true def
    {
        s2a counterify /mk exch def
        first {
            /mc mk def
            /first false def
        } {
            mc keys {
                /k exch def
                mk k known {
                    mc k 2 copy get mk k get min put
                } {
                    mc k undef
                } ifelse
            } forall
        } ifelse
    } forall
    [
        mc keys quicksort {
            /c exch def
            c 1 array astore a2s /s exch def
            mc c get {
                s
            } repeat
        } forall
    ]
    end
} bind def

(commoncharacters) test.start
[(bella) (label) (roller)] commoncharacters [(e) (l) (l)] deepeq test
[(cool) (lock) (cook)] commoncharacters [(c) (o)] deepeq test
[(hello) (world) (pole)] commoncharacters [(l) (o)] deepeq test
[(abc) (def) (ghi)] commoncharacters [] deepeq test
[(aab) (aac) (aaa)] commoncharacters [(a) (a)] deepeq test
test.end