%!PS

% begin included library code
% see https://github.com/Firedrake/postscript-libraries/
/apop.right { % [a b c] -> [a b] c
    [ exch aload length 1 add 1 roll ] exch
} 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

/quicksort { % [ a c b ] -> [ a b c ]
    1 dict begin
    /arr exch def
    arr length 0 gt {
        0 arr length 1 sub quicksort.main
    } if
    arr
    end
} 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.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 ge {
                exit
            } if
        } loop
        {
            /j j 1 sub def
            arr j get pivot le {
                exit
            } if
        } loop
        i j ge {
            j
            exit
        } if
        i j quicksort.swap
    } loop
    end
} bind def

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

/apop.left { % [a b c] -> [b c] a
    dup 0 get exch
    [ exch aload length -1 roll pop ] exch
} 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


% end included library code

/is_wigglesorted {
    2 dict begin
    /l exch def
    true
    0 1 l length 2 sub {
        /i exch def
        i 2 mod 0 eq {
            l i get l i 1 add get ge {
                pop false exit
            } if
        } {
            l i get l i 1 add get le {
                pop false exit
            } if
        } ifelse
    } for
    end
} bind def

/wigglesort {
    6 dict begin
    /s exch quicksort def
    /lg s length def
    /p lg 2 idiv def
    /a [ 0 1 p 1 sub { s exch get } for ] def
    /b [ p 1 lg 1 sub { s exch get } for ] def
    /i 0 def
    [
        lg 2 mod 1 eq {
            b apop.left exch /b exch def
            /i 1 def
        } if
        i 1 lg 1 sub {
            2 mod 0 eq {
                a apop.right exch /a exch def
            } {
                b apop.right exch /b exch def
            } ifelse
        } for
    ]
    end
} bind def

(wigglesort) test.start
[ 1 5 1 1 6 4 ] is_wigglesorted not test
[ 1 6 1 5 1 4 ] is_wigglesorted test
[ 1 3 2 2 3 1 ] is_wigglesorted not test
[ 2 3 1 3 1 2 ] is_wigglesorted test
[ 1 3 2 2 3 1 ] is_wigglesorted not test
[ 1 5 1 1 6 4 ] wigglesort is_wigglesorted test
[ 1 3 2 2 3 1 ] wigglesort is_wigglesorted test
[ 1 3 2 2 2 3 1 ] wigglesort is_wigglesorted test
test.end