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In this contest, I had solved 6 (1 unofficial) challenges.
AP Lab English Language
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This challenge gave us a script that done something like swap index
of characters of the input. After that, if input is equal to
"1dd3|y_3tttb5g`q]^dhn3j" , the input is correct.
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For the algorithms, transpose function choose new
character for each character in "ret" base on
"input" and "transpose". Then, all characters
xor with numbers corresponding. Do it for three times.
- For example,
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input = "abcxyz"
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transpose = {4, 2, 3, 1, 0, 5}
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Then, ret = "ycxbaz"
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For the solution, if I have "ret" string, I can get
the previous string.
- There are two ways to solve.
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First solution: reverse the action.
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Second solution: for each order, trying all
printable character, follow the exactly step of source,
and then compare.
AP Lab Computer Science Principles
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This challenge requests "input", decreases each char with its
order and plus with the length of the character as decimal number on
ascii table.
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For the solution, with each order, I try all possible printable char
and do exactly the action of source code.
dis
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I received a disassembly of python code named "disas".
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Depend on some documents on the Internet, I knew how the disassembly
code show out.
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In short:
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LOAD_FAST: local variable.
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LOAD_GLOBAL: global variable, function.
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LOAD_CONST: number.
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FOR_ITER 24 (to 48): for loop from line 24 to line 48.
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CALL_FUNCTION n: call the function was LOAD_GLOBAL in n+1
previous line. Arguments are n nearest line.
- This is original python code after rewrite.
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This is solution when I reversed all calculation.
Ice Cream Bytes
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In short:
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First, java file read and collect some characters from
IceCreamManual.txt in function fillMachine().
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Second, input run through numbers of function and compare with
previous string which returned from function
fillMachine().
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For the solution, we need reverse the processing:
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toppings(chocolateShuffle(vanillaShuffle(strawberryShuffle(input))))
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To this:
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strawberryShuffle(vanillaShuffle(chocolateShuffle(toppings(string))))
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Also, all calculations in those functions must be reversed.
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Here is the
script.
Recursion Reverse
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For the algorithms, script get the input and then put it
into flagTransformed().
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Each character plus with pickNum( its_index (or i) ):
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Calculate sum of first i number.
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If it is even then return the num else continue call new
function.
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Note:
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When order equal to 11, num will very very big and if we
use for loop, time is very slowly. To deal with it, I replaced it
with O(1) calculation.
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The type of num is int32, that means I have to use
numpy.uint32 in order to convert num to int32 number before
return.
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As usual, for the solution, I try all printable character on each
index, calculate and compare with the given string.
AP Lab 3D Design (unofficial)
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Input receives 25 character, then splits into 5x5 matrix, each of
them are converted to 8 bit binary. As a result, we have 5x5x8
matrix.
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Next, for each order in binary number, function
shuffle1() will swap the corresponding binary bit in each element of that row together.
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Finally, shufle2() will xor the corresponding element.
- For the solution, I just xor and re-swap with the correct position.
- Because of some reasons, author did not upload the challenge again, so that I could not test my solution. Perhaps it is right.
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