I have been thinking to solve any problem like 1+2*4-5 with user entering it and program to solve it. I've read some questions on this site about storing arithmetic operator and the solution says to check by using switch which can't be applied here. I would be thankful if anybody could suggest any idea of how to make it.
I had a similar exercise not long ago, but in the question it was stated that the seperation is a space. So the user input would be 1 + 2 * 4 - 5, and i solved it that way. I will give you some tips but not paste the whole code.
-you read the input as a String
-you can use the String.split() method to devide the String into the pieces you need and they will be put in an array.(in this case: strArray[0]='1',strArray[1]='+', etc)
-you will need a for-loop to go trough every String in the array:
-the decimals will need to be converted to integers with the Integer.parseInt() method.
-The + - * / will need to be put in switch-statement.
(be careful how you construct your loop, think about how many times you want to go trough it and what you need in each loop)
I hope these tips helped.
Related
so I've been working on a task. I have two giant strings, both consist of the same characters just scrambled. The task is to find the lowest possible number of changes you can make to turn the first string in the other one, while 1 change = switching neighbour chars in the string. I found a solution that works just fine but there is a problem. It works under 5 seconds only for input of about 100 000 char Strings. I need to make it work for up to 1000 000 char. I tried ArrayList, LinkedList, regular arrays, substrings and different variations of the algorythm, this one is the best so far I came up with but I'm out of ideas. Any help? Is there a faster collection I can use? Maybe the algoryth is wrong here?
"jas" ArrayList is the first string converted into a list
"mal" is the other one. "steps" is the output
int steps=0;
int index=0;
while(jas.size()>1) {
if(jas.get(0)!=mal.get(index)) {
int distance = jas.indexOf(mal.get(index));
jas.remove(distance);
steps+=distance;
} else {
jas.remove(0);
}
index++;
}
System.out.println(steps);
Thanks in advance for any ideas!
I know its a bit off topic here (you should go to codereview) but idea I got is to use something already implemented in Java like:
listToSort.sort(Comparator.comparing(listWithOrder::indexOf));
Go to functions the function and look at them and you can either take them out and create your own based on that and put a counting there or inspire by it.
I believe that whatever is implemented there is probably very fast.
I've been searching around and havn't quite found my answer.
At this moment me and along with my group have created a few classes resembling a Bank with Customer and Account and so on.
I've been struggling lately with trying to improve and secure our code by making our variable called "name" only respond to certain inputs.
In this case, I want to make it only possible for the person to enter name as such:
Atleast 2 words = (For the word part I've seen codes where you count towards the white space between but don't know yet what you do about the last word since there wont be a white space)
Max 4 words = ( Same thing here)
No special signs such as ,!%¤"#()=%/'¨. = ( for this, I've read something about "Matcher and pattern" )
Now I'm quite new to Java and I'm not asking for a code from someone, I'm asking for someone to point me in the right directions regarding codes, because alot of what i've seen like the Matcher and pattern are things that you import with downloading utils and stuff but I reckon that it's not needed and there should be a simpler more basic way as I'm not trying to get ahead of myself with copying codes just to get it done.
So yeah, the String "name" is used alot in our main class "Banklogic" where almost every method that adds something has the variable "name" in it, so it's quite important that I get this done.
I hope I was clear enough and any help would be appreciated! I'm gonna put the alarm for 3 hours before school to see what you guys have come up with so I can try and complete the code before our meeting! Thanks alot in advance :)
Since you asked for hints, you can use Regex to add such rules.
For Numbers only:
if(string.matches("[0-9\\W]")
//allow insertion of data else not
As for rules related Word Count:
string.split("\\W") will create an array separated by space character. You can count the number of elements in this array and allow/disallow input based on that.
As for no signs and only letters:
if(string.matches("[a-zA-Z\\W]")
// Allow Input else not
You can use Document Filter to implement these methods. Document filter will only allow text to be entered if you allow it to.
I hope this helped as a hint.
Also, note that \\W is for whitespaces. If you dont want to allow whitespaces, remove that char.
This is the most effective and simple way of doing the task.
EDIT:
This is a Class I wrote a little while ago to achieve such tasks. Just in case if you are interested....
I have the following piece of code called Code1.
http://pastebin.com/tc0Vd8xh
When I run this, the sketch does not work.
However when I replace "i=+50" for "i = i + 50" the code works.
My question is why the "i=+50" bit does not work?
As far as I know "i=+50" is proper Java and Processing is based on Java.
I tried to Google about "i=+50" but Google does not process non-alphanumeric characters.
So I came here and I searched in previous questions before asking here. Anyone, any idea why "i=+50" does not work?
The statement i=+50 is the assignment of positive 50 to i. That is why it compiles, but doesn't add 50 to i on each loop. As #RoelHarbers and #ByoTic mentioned, you actually want i += 50
You're using =+, which is not a java operator (or an operator in any other language I know of)
The proper syntax is:
i+=50
Because it's i+=50 and not i=+50.
i =+ 50 is not going to do what you want, it is going to initialize i with 50. Instead, use i+=50, this going to add the 50 to whatever value that i holds.
Now this is a tricky problem for which I'm not able to figure out a good solution. Suppose we have a String in Java:- "He ate 3 apples today." Now the digit 3 can be easily identified in Java using isNumeric function or using regular expressions. But what if I have a String like: "He ate three apples today."? How can I identify that three is actually a number? I used OpenNlp and used its POS tagger but the time it takes to do is really too much! Can anyone suggest a better solution for this? Also among the ".bin" of OpenNlp, there is one file-"num.bin", but I don't know how to use this file. OpenNlp documentation also say nothing about it. Can anyone tell me if this is exactly what I've been looking for, and if yes then how to use it.
/*********************************************************************************************************************************/
I'm actually short of time here, so I've settled on a temporary solution here. Make a file/dictionary and take all the entries in a hashtable. Then I'll tokenize my sentence and check word by word for numbers, similar to what you guys suggested. I'll keep on updating the file as and when required. Thanks for your valuable suggestions guys, and if you have got something better than this I'd be really glad. OpenNlp implements this in a very good way, the only problem with it is time complexity and I want to do this in minimum time possible.
Create a dictionary of numbers. Search for elements from that dictionary in the text.
Check asympotic complexity, it may be cheaper to sort the text first.
You have to keep all that words in arrays and then use it. Here is an example how to convert number to string. It may help you... I think you have to split your text into words and check if a word is a number (three). If yes check the next word because it can be say "million", then check the next word and so on. It's not easy and seems like a little library.I think you'll spend a lot of time writing this. Or try to search in google for a library like this. Maybe someone have already got this problem, wrote a library and shares it for free )) Good luck.
I have to keep in mind the priority of operations, all the numbers including the answer are integers (seems silly to me but whatever), and I have to parse a String for the equation and, as far as I'm aware, push each number and each operator in two different stacks before I compare them.
I don't know how to approach this problem, and right now my main concern is dealing with parentheses. I want to use a recursive method to solve the calculation which would check for parentheses and solve them and replace them with their result, but I'm not sure how to do that. I could use substring() and indexOf() but I'd rather be more elegant.
Other than that I'm not sure how to solve the calculation once numbers and operators are stacked. I think I should compare the top 2 operators to make sure that if I combine two numbers, it is in the right order of operations, but I don't want to be clumsy with that part either.
My recommendation would be that you study the Shunting-yard algorithm and come back when you have specific questions about how it works or how to implement certain parts of it.