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Problem solution · Turing

CCC 1999 P2 - Year 2000

CCC 1999 P2 - Year 2000: a Turing solution using direct simulation. Learn the idea, check the complexity, and read the full code, with credit to CCCSolutions.

Technique
Direct simulation
Source
CCCSolutions
Length
157 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Direct simulation

For CCC 1999 P2 - Year 2000, the implementation follows the problem’s operations directly while maintaining only the state needed for the next decision.

  1. Translate each rule into one explicit state update.
  2. Maintain the invariant after every processed item.
  3. Return the accumulated state once all relevant input has been handled.

Code notes

  • 157 lines of Turing from the credited upstream file ccc99s2.t.
  • The implementation keeps its working state in language-native values and containers.
  • No explicit loop blocks detected.

Complexity

Count the number and nesting of passes over the input, then include the maintained containers in the memory estimate.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from CCCSolutions by CCCSolutions contributors · Milliken Mills High School and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeCCC 1999 P2 - Year 2000 · TuringTuring
Use this to learn the idea, then write your own version.
% CCC 1999% problem B: Year 2000%% read a series of lines and find dates of the format% dd/mm/yy or yy.mm.dd or month dd, yy% no letter or digits preceeding or following% dd is 01-31, mm is 01-12 and yy is 00-99 % change yy to 20yy if y < 25 and 19yy otherwise % UGLY problem, ALL the different cases need to be looked for! % file handling is used, the number of lines is given var infile : string := "y2k.in"var outfile : string := "y2k.out"var fi, fo : intvar n : intvar line : string %returns true if a string is a letter or numberfunction dn (s : string (1)) : boolean    if s >= "a" and s <= "z" or            s >= "A" and s <= "Z" or            s >= "0" and s <= "9" then        result true    else        result false    end ifend dn % process the line for dd/mm/yy given a starting locationprocedure dmy (i : int, var s : string)    if i > 1 and dn (s (i - 1)) then     elsif i + 8 <= length (s) and dn (s (i + 8)) then     elsif i + 7 > length (s) then     elsif strintok (s (i .. i + 1)) and strint (s (i .. i + 1)) >= 1 and            strint (s (i .. i + 1)) <= 31 and            s (i + 2) = "/" and            strintok (s (i + 3 .. i + 4)) and strint (s (i + 3 .. i + 4)) >=            1 and strint (s (i + 3 .. i + 4)) <= 12 and            s (i + 5) = "/" and            strintok (s (i + 6 .. i + 7)) and strint (s (i + 6 .. i + 7)) >=            0 and strint (s (i + 6 .. i + 7)) <= 99 then        if strint (s (i + 6 .. i + 7)) < 25 then            s := s (1 .. i + 5) + "20" + s (i + 6 .. *)        else            s := s (1 .. i + 5) + "19" + s (i + 6 .. *)        end if    end ifend dmy % process the line for yy.mm.dd given a starting locationprocedure ymd (i : int, var s : string)    if i > 1 and dn (s (i - 1)) then     elsif i + 8 <= length (s) and dn (s (i + 8)) then     elsif i + 7 > length (s) then     elsif strintok (s (i .. i + 1)) and strint (s (i .. i + 1)) >= 0 and            strint (s (i .. i + 1)) <= 99 and            s (i + 2) = "." and            strintok (s (i + 3 .. i + 4)) and strint (s (i + 3 .. i + 4)) >=            1 and strint (s (i + 3 .. i + 4)) <= 12 and            s (i + 5) = "." and            strintok (s (i + 6 .. i + 7)) and strint (s (i + 6 .. i + 7)) >=            1 and strint (s (i + 6 .. i + 7)) <= 31 then        if strint (s (i .. i + 1)) < 25 then            s := s (1 .. i - 1) + "20" + s (i .. *)        else            s := s (1 .. i - 1) + "19" + s (i .. *)        end if    end ifend ymd % process the line for Month dd, yy given a starting locationprocedure mdy (i : int, var s : string)    if i > 1 and dn (s (i - 1)) then     else        var x : int        if i + 6 <= length (s) and s (i .. i + 6) = "January" then            x := i + 7        elsif i + 7 <= length (s) and s (i .. i + 7) = "February" then            x := i + 8        elsif i + 4 <= length (s) and s (i .. i + 4) = "March" then            x := i + 5        elsif i + 4 <= length (s) and s (i .. i + 4) = "April" then            x := i + 5        elsif i + 2 <= length (s) and s (i .. i + 2) = "May" then            x := i + 3        elsif i + 3 <= length (s) and s (i .. i + 3) = "June" then            x := i + 4        elsif i + 3 <= length (s) and s (i .. i + 3) = "July" then            x := i + 4        elsif i + 5 <= length (s) and s (i .. i + 5) = "August" then            x := i + 6        elsif i + 8 <= length (s) and s (i .. i + 8) = "September" then            x := i + 9        elsif i + 6 <= length (s) and s (i .. i + 6) = "October" then            x := i + 7        elsif i + 7 <= length (s) and s (i .. i + 7) = "November" then            x := i + 8        elsif i + 7 <= length (s) and s (i .. i + 7) = "December" then            x := i + 8        else            x := 99999        end if        if x + 7 <= length (s) and dn (s (x + 7)) then         elsif x + 6 > length (s) then         elsif s (x) = " " and                strintok (s (x + 1 .. x + 2)) and strint (s (x + 1 .. x +                2)) >= 1 and                strint (s (x + 1 .. x + 2)) <= 31 and                s (x + 3 .. x + 4) = ", " and                strintok (s (x + 5 .. x + 6)) and strint (s (x + 5 .. x +                6)) >= 0 and strint (s (x + 5 .. x + 6)) <= 99 then            if strint (s (x + 5 .. x + 6)) < 25 then                s := s (1 .. x + 4) + "20" + s (x + 5 .. *)            else                s := s (1 .. x + 4) + "19" + s (x + 5 .. *)            end if        end if    end ifend mdy  open : fi, infile, getopen : fo, outfile, putget : fi, nfor i : 1 .. n    get : fi, line : *    var j : int := 1    loop        exit when j >= length (line)        dmy (j, line)        ymd (j, line)        mdy (j, line)        j := j + 1    end loop    put : fo, lineend for close : ficlose : fo

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