This is my first post so please comment down if you need further clarification, Say we take in a string such as:
((((a).(5)).((a)*)).((b)*))*
and through the process, we perhaps count++ the amount of '(' read and count-- the amount of ')' read until we come across our first char or variable (we can consider other operators such as '.' or '|' or '*') that is the left and innermost content such that a is replaced so that our string now reads:
(((R1.(5)).((a)*)).((b)*))*
We must consider when a is selected, we also include its parenthesis as well but only consider the string that is read (perhaps store it in or as a vector, pointer, object, etc.), the same applies for when 5 which results in:
(((R1.R2).((a)*)).((b)*))*
at this moment we perhaps find now that the innermost content found is string (R1.R2) and
this results the string to be converted into R3 and having the string as:
((R3.((a)*)).((b)*))*
We continue the iteration for a to be read too.
((R3.(R4*)).((b)*))*
If a star * is read, we can consider extracting that content with R4 to be replaced as R5
((R3.R5).((b)*))*
Our next iteration follows:
((R3.R5).(R6*))*
((R3.R5).R7)*
(R8.R7)*
R9*
and finally as our final result,
R10
And we end.
I've already tried a variety of algorithms from several sources for hours yet I'm still stuck and puzzled at the same spot and I may not be thinking this through very properly as I had hoped.
The only closest that was modified was this:
https://www.geeksforgeeks.org/extract-substrings-between-any-pair-of-delimiters/
but I'm still puzzled about what must be properly implemented.
How would you make this possible? Any solutions or a straight post of your code could surely help me understand this process.
Related
I have different commands my program is reading in (i.e., print, count, min, max, etc.). These words can also include a number at the end of them (i.e., print3, count1, min2, max6, etc.). I'm trying to figure out a way to extract the command and the number so that I can use both in my code.
I'm struggling to figure out a way to find the last element in the string in order to extract it, in Smalltalk.
You didn't told which incarnation of Smalltalk you use, so I will explain what I would do in Pharo, that is the one I'm familiar with.
As someone that is playing with Pharo a few months at most, I can tell you the sheer amount of classes and methods available can feel overpowering at first, but the environment actually makes easy to find things. For example, when you know the exact input and output you want, but doesn't know if a method already exists somewhere, or its name, the Finder actually allow you to search by giving a example. You can open it in the world menu, as shown bellow:
By default it seeks selectors (method names) matching your input terms:
But this default is not what we need right now, so you must change the option in the upper right box to "Examples", and type in the search field a example of the input, followed by the output you want, both separated by a ".". The input example I used was the string 'max6', followed by the desired result, the number 6. Pharo then gives me a list of methods that match that:
To get what would return us the text part, you can make a new search, changing the example output from number 6 to the string 'max':
Fortunately there is several built-in methods matching the description of your problem.
There are more elegant ways, I suppose, but you can make use of the fact that String>>#asNumber only parses the part it can recognize. So you can do
'print31' reversed asNumber asString reversed asNumber
to give you 31. That only works if there actually is a number at the end.
This is one of those cases where we can presume the input data has a specific form, ie, the only numbers appear at the end of the string, and you want all those numbers. In that case it's not too hard to do, really, just:
numText := 'Kalahari78' select: [ :each | each isDigit ].
num := numText asInteger. "78"
To get the rest of the string without the digits, you can just use this:
'Kalahari78' withoutTrailingDigits. "Kalahari"6
As some of the Pharo "OGs" pointed out, you can take a look at the String class (just type CMD-Return, type in String, hit Return) and you will find an amazing number of methods for all kinds of things. Usually you can get some ideas from those. But then there are times when you really just need an answer!
i just have a quick question on this bit of code i have here on the Cryptopals Challenges, using Python3, For XORing a string with one single character.The program takes in a hex string string, decodes it, XORs it with a single character, does this for every possible character, then finds the "most english" line of XORd data. heres my code snippet (which i admittdly used from a solutions page ) :
def singlechar_xor(input_bytes, key_value):
"""XORs every byte of the input with the given key_value and returns the result."""
output = b''
for char in input_bytes:
output += bytes([char ^ key_value])
return output
i know what is happening and i understand what is supposed to happen, im just not sure how bytes behave and what types are and arent supposed to be XORd. Why do i need the brackets around char^key_value? If i remove the brackets my output becomes a bunch of 0's. What is the result of the XOR or the character and the key_value? If someone could kindly explain so i could have a better understanding going forward in these challenges id GREATLY appreciate it <3
In TI-BASIC, the + operation is overloaded for string concatenation (in this, if nothing else, TI-BASIC joins the rest of the world).
However, any attempt to concatenate involving an empty string raises a Dimension Mismatch error:
"Fizz"+"Buzz"
FizzBuzz
"Fizz"+""
Error
""+"Buzz"
Error
""+""
Error
Why does this occur, and is there an elegant workaround? I've been using a starting space and truncating the string when necessary (doesn't always work well) or using a loop to add characters one at a time (slow).
The best way depends on what you are doing.
If you have a string (in this case, Str1) that you need to concatenate with another (Str2), and you don't know if it is empty, then this is a good general-case solution:
Str2
If length(Str1
Str1+Str2
If you need to loop and add a stuff to the string each time, then this is your best solution:
Before the loop:
" →Str1
In the loop:
Str1+<stuff_that_isn't_an_empty_string>→Str1
After the loop:
sub(Str1,2,length(Str1)-1→Str1
There are other situations, too, and if you have a specific situation, then you should post a simplified version of the relevant code.
Hope this helps!
It is very unfortunate that TI-Basic doesn't support empty strings. If you are starting with an empty string and adding chars, you have to do something like this:
"?
For(I,1,3
Prompt Str1
Ans+Str1
End
sub(Ans,2,length(Ans)-1
Another useful trick is that if you have a string that you are eventually going to evaluate using expr(, you can do "("+Str1+")"→Str1 and then freely do search and replace on the string. This is a necessary workaround since you can't search and replace any text involving the first or last character in a string.
First and foremost, I'm not familiar with Perl at all. I've been studying C++ primarily for the last 1/2 year. I'm in a class now that that is teaching Linux commands, and we have short little topics on languages used in Linux, including Perl, which is totally throwing me for a loop (no pun intended). I have a text file that contains a bunch of random numbers separated by spaces and tabs, maybe even newlines, that gets read into the program via a filehandle. I'm supposed to write 2 lines of code that split the lines of numbers and merge them into one array, inside of a foreach loop. I'm not looking for an answer, just a nudge in the right direction. I've been trying different things for multiple hours and feel totally silly I can't get it, I'm totally lost with the syntax. Its just a bit odd not working inside a compiler and out of my comfort zone working outside of C++. I really appreciate it. I've included a few photos. Basically, the code we are writing it just to store the numbers and the rest of the program will determine the smallest number and sum of all numbers. Mine is currently incorrect because I'm not sure what to do. In the output photo, it will display all the numbers being entered in via the text file, so you can see them.
Several things to fix here. First of all, please don't post screenshots of your sample data or code, as it makes it impossible to copy and paste to test your code or data. Post your code/data by indenting it with four spaces and a newline preceding the code block.
Add use strict; in your script. This should be lesson 0 in your class. After that add my to all variable declarations.
To populate #all_numbers with contents of each line's numbers, without using push, you can use something like this:
foreach my $line (#output_lines)
{
my #numbers = split /\s/, $line;
#all_numbers = (#all_numbers, #numbers);
}
You say you're "not looking for an answer," so here's your nudge:
You're almost there. You split each line well (using split/\s/) and store the numeric values in #all_numbers. However, notice that each time around in the loop, you replace (using the assignment, #all_numbers = ...) the whole contents of #all_numbers with the numbers you found in the current line. Effectively, you're throwing away everything you've stored from the previous lines.
Instead, you want to add to #all_numbers, not replace #all_numbers. Have a look at the push() function for how to do this.
NB: Your split() call is fine, but it's more customary to use split(' ', $line) in this case. (See split(): you can use a single space, ' ', instead of the pattern, /\s/, when you want to split on any whitespace.)
I hope you need to store the all splitting element into array, so you looking for push function.
foreach $line (#input_lines)
{
push(#all_numbers,split(/\s/,$line));
}
Your problem is, in every iteration, the splitted value is over written in an array not to append together. For example,
#array = qw(one two three);
#array = qw(five four seven);
print "#array";
output is five four seven not the one two three five four seven because this is reinitialize with a new values. You want to append the new values in the array in before or after use unshift or push
for example
#array = qw(one two three);
push(#array,qw(five four seven));
Another way:
my #all_numbers = map { split ' ', $_ } #output_lines;
See http://perldoc.perl.org/functions/map.html
I have to write a MATLAB function with the following description:
function counts = letterStatistics(filename, allowedChar, N)
This function is supposed to open a text file specified by filename and read its entire contents. The contents will be parsed such that any character that isn’t in allowedChar is removed. Finally it will return a count of all N-symbol combinations in the parsed text. This function should be stored in a file name “letterStatistics.m” and I made a list of some commands and things of how the function should be organized according to my professors' lecture notes:
Begin the function by setting the default value of N to 1 in case:
a. The user specifies a 0 or negative value of N.
b. The user doesn’t pass the argument N into the function, i.e., counts = letterStatistics(filename, allowedChar)
Using the fopen function, open the file filename for reading in text mode.
Using the function fscanf, read in all the contents of the opened file into a string variable.
I know there exists a MATLAB function to turn all letters in a string to lower case. Since my analysis will disregard case, I have to use this function on the string of text.
Parse this string variable as follows (use logical indexing or regular expressions – do not use for loops):
a. We want to remove all newline characters without this occurring:
e.g.
In my younger and more vulnerable years my father gave me some advice that I've been turning over in my mind ever since.
In my younger and more vulnerableyears my father gave me some advicethat I’ve been turning over in my mindever since.
Replace all newline characters (special character \n) with a single space: ' '.
b. We will treat hyphenated words as two separate words, hence do the same for hyphens '-'.
c. Remove any character that is not in allowedChar. Hint: use regexprep with an empty string '' as an argument for replace.
d. Any sequence of two or more blank spaces should be replaced by a single blank space.
Use the provided permsRep function, to create a matrix of all possible N-symbol combinations of the symbols in allowedChar.
Using the strfind function, count all the N-symbol combinations in the parsed text into an array counts. Do not loop through each character in your parsed text as you would in a C program.
Close the opened file using fclose.
HERE IS MY QUESTION: so as you can see i have made this list of what the function is, what it should do, and using which commands (fclose etc.). the trouble is that I'm aware that closing the file involves use of 'fclose' but other than that I'm not sure how to execute #8. Same goes for the whole function creation. I have a vague idea of how to create a function using what commands but I'm unable to produce the actual code.. how should I begin? Any guidance/hints would seriously be appreciated because I'm having programmers' block and am unable to start!
I think that you are new to matlab, so the documentation may be complicated. The root of the problem is the basic understanding of file I/O (input/output) I guess. So the thing is that when you open the file using fopen, matlab returns a pointer to that file, which is generally called a file ID. When you call fclose you want matlab to understand that you want to close that file. So what you have to do is to use fclose with the correct file ID.
fid = open('test.txt');
fprintf(fid,'This is a test.\n');
fclose(fid);
fid = 0; % Optional, this will make it clear that the file is not open,
% but it is not necessary since matlab will send a not open message anyway
Regarding the function creation the syntax is something like this:
function out = myFcn(x,y)
z = x*y;
fprintf('z=%.0f\n',z); % Print value of z in the command window
out = z>0;
This is a function that checks if two numbers are positive and returns true they are. If not it returns false. This may not be the best way to do this test, but it works as example I guess.
Please comment if this is not what you want to know.