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Algorithms

An algorithm is a self-contained step-by-step set of operations to be performed. Algorithms exist that perform calculation, data processing, and automated reasoning. Starting from an initial state and initial input (perhaps empty), the instructions describe a computation that, when executed, proceeds through a finite number of well-defined successive states, eventually producing "output" and terminating at a final ending state. The transition from one state to the next is not necessarily deterministic; some algorithms, known as randomized algorithms, incorporate random input.

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What options are there to protect a web service from a DOS attack?

IF the web service were accessed only by my Objective-C iPhone application, and nowhere else, is this web service protected by the "security through obscurity" model? Or, can hackers crack open the source code of the iPhone app, like Apple can?

What about if I put the URL to the web service into the SQLite database and encrypted the Path?

So, when my app needs to request information from the web service, it does a DB lookup in the SQLite database for the path to the web service. When it gets it, it decrypts it. Then, using a variable (in memory) only, it makes the web service call.

Does this protect from a DOS attack to that web service call?

Are there easier ways?

Will this work on Java for the Android?

What about on my website?

Thanks.
0
Free Tool: Subnet Calculator
LVL 10
Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

What technologies are best suited for the highest performance web services to handle the heaviest loads? Thousands (even millions) of transactions per second?

I know that Node.js can handle thousand(s) sessions on a single thread. And I do not know of any other technology which handle more than one session per thread. Am I right about that? Are there others that can do this also?

What about real-time programming as it relates to web-services. Is there such a thing?

And how about a few general words about hardware deployment? Having a central API call which distributes calls to hundreds of more specialized web servers? What about Caching for successive related calls?

And what about Machine Learning? Can algorithms be optimized by existing Machine Learning algorithms that reduce the average response times of the most heavily load web service?

Thanks.
0
What should I expect by forking the BitCoin open source code? What kinds of things can one do in customizing the code?

What language(s) is it in? What platform does it run on?

What about the code run by Bookkeepers? And the generation of the BlockChain database updates?

And lastly, what "engine" determines which algorithms need to be mined and what is managing the connections to this peer-to-peer network?

Thanks
0
I have the Excel file below with 3 columns.
On one row I have a pair of q, k corresponding to a certain x.
In the sheet are different values for x.
I need to find what pairs of q, k are common for all values of x.
How do you do that fast and easy?
Pairs.xlsx
0
What is the best and easiest approach, method, software to solve a system like the one below?

1=1*(3.14*2^p-1*1*[(23.14-5)*2^q-1*1*(3.14-3)/2^k]/2^r)/2^s
3=8*(3.14*2^p-8*8*[(23.14-5)*2^q-8*8*(3.14-3)/2^k]/2^r)/2^s
50=128*(3.14*2^p-128*128*[(23.14-5)*2^q-128*128*(3.14-3)/2^k]/2^r)/2^s
2896=8192*(3.14*2^p-8192*8192*[(23.14-5)*2^q-8192*8192*(3.14-3)/2^k]/2^r)/2^s
4096=16384*(3.14*2^p-16384*16384*[(23.14-5)*2^q-16384*16384*(3.14-3)/2^k]/2^r)/2^s

Could you help to find a set of solutions? I guess are more than one.
This is not homework, but rather one of that engineering approximation problem that ended up in a set of unknown variables.

Basically the function is.
S5(x)=x*(PI*2^p-x*x*[(2PI-5)*2^q-x*x*(PI-3)/2^k]/2^r)/2^s
with p, q, k, r, s unknown.
And next known set of solutions with 1 digit approximation allowed for S5x:
x - S5x
1 - 0
2 - 1
4 - 2
8 - 3
16 - 6
32 - 13
64 - 25
128 - 50
256 - 101
512 - 201
1024 - 401
2048 - 799
4096 - 1567
8192 - 2896
16384 - 4096
0
Hey,

I have an audio file, many actually, that are an interview between the interviewer and interviewee.  The same person is asking questions in each file, while the people answering are different.

I need to separate the answers out by generating silence over the interview questions. I'm currently doing this by hand with audacity, but it is extremely time consuming.

Any help would be greatly appreciated.  I am a software developer, but audio is not my area, so code is am option if there isn't a program available.

Thanks
0
If I am comparing my algorithm to another algorithm. My algorithm has a complexity f O(n) whereas the other algorithm is O(n2).

I then measured the running time by implementing the algorithms.

Should the running time of the other algorithm be the square of the running time of my algorithm?

For example of my algorithm running time is 3 ms should the other algorithm running time be 9?
0
I got a requirement from my client that he wishes to encrypt/ password protect some of the documents, before sending over to another user in another regional office.

By not writing the password into the email body.

How can the user in another regional office knows the password to decrypt/ open the protected documents?

What approach should be adopted? Is there any standard/ algorithm I can refer to? But we prefer not to use any 3rd party software/ utility.

Thank you.
0
the array has series of numbers Need to find all pairs in the array using a hash table
integers ...
0
The problem: I want to display a row of rectangles placed shoulder to shoulder, on a grid page (think graph paper). The width of the page where the rectangles appear will be an unknown integer variable (but always greater than 100).  The height of the rectangles will be a constant integer value (e.g., 20 units high). I want to fill a row on this page with as many rectangles as possible where the rectangle width will be equal or greater than the predefined rectangle height and where there will be no gap/margin at the end of the row.

I realize that this is only possible when the page width (e.g. 200)  can be evenly divided by the rectangle height (e.g., 200 / 20).  If the page width is 201, it is impossible to have rectangles all with the same width and at the same time have no gap/margin at the end of the row of rectangles. But if the page width is 210, I can fit 10 rectangles which are 21 units wide. That's fine. I don't mind stretching the rectangles a bit, as long as the rectangle width is never less than the predefined rectangle height constant (in this example, is 20). So, if the page width is 220, that works fine for I can get 10 rectangles of 22 units across the page with no gap/margin at the end of the row. I don't mind the rectangle width growing a bit so as to ensure no right margin/gap results. But there would be a limit to the rectangle width changing from its original desired width (which is equal to the rectangle height constant).  So I would need the …
0
Free Tool: Path Explorer
LVL 10
Free Tool: Path Explorer

An intuitive utility to help find the CSS path to UI elements on a webpage. These paths are used frequently in a variety of front-end development and QA automation tasks.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

I have an array that will have approx 3000 elements. Within each element is an array that contains two key:value pairs. I want to sort the elements of the outer array based on the value of the first key:value pairs within each element.

e.g.
array = [{"key1":"group9","key2":["20170222","20170531"]},{"key1":"group3","key2":["20170221"]},{"key1":"group7","key2":["20170321"]}, ..................]

so sorting gives e.g. (the elements are arranged based on sorting the groupX value of key key1 i.e. the first key:value pair)

array = [{"key1":"group3","key2":["20170221"]} ,{"key1":"group7","key2":["20170321"]} ,{"key1":"group9","key2":["20170222","20170531"]},................................]


I've implemented a merge sort and it works fine. But I want to look at what is the most efficient algorithm to use, as my colleagues have suggested bubble sort (I thought this was one of the worst algorithms, but it really depends on how large the dataset is).

Can anyone advise?

I'll (learn to) implement this on a webpage so I'm using Javascript/JQuery/ReactJS
0
I know that a circle has 360 degrees and Pi has a very specific an known value.

The question is, must a circle had 360 degrees? Or was that a decision that was made so each quarter would have 90 degrees?

So, was Pi "backed into"?

If Euclid had wanted a circle to be 400 degrees, could he have simply used a different formula to generate Pi?

Curious.

And what is that formula to generate Pi, if you have it.

Thanks
0
Hello,
I need some help with this code. It works for some Arrays but not for all. Do you see a mistake in the code?

These are the failures of 13 different tests:
  There were 3 failures:
  1) test3(ads.set2.knapsack.test.EfficientKnapsackTest)
  java.lang.AssertionError: Checking optimal profit:  expected:<3144> but was:<2660>
  ?at ads.set2.knapsack.test.EfficientKnapsackTest.performTests(EfficientKnapsackTest.java:157)
  ?at ads.set2.knapsack.test.EfficientKnapsackTest.test3(EfficientKnapsackTest.java:69)
  2) test4(ads.set2.knapsack.test.EfficientKnapsackTest)
  java.lang.AssertionError: Checking optimal profit:  expected:<76> but was:<72>
  ?at ads.set2.knapsack.test.EfficientKnapsackTest.performTests(EfficientKnapsackTest.java:157)
  ?at ads.set2.knapsack.test.EfficientKnapsackTest.test4(EfficientKnapsackTest.java:74)
  3) test8(ads.set2.knapsack.test.EfficientKnapsackTest)
  org.junit.runners.model.TestTimedOutException: test timed out after 300 milliseconds

  FAILURES!!!
  Tests run: 13,  Failures: 3



public class KnapsackSolver {

	/**
	 * Calculates the maximum profit for the knapsack problem using 
	 * an improved dynamic programming algorithm
	 * 
	 * @param items
	 *            the items available to be packed into the knapsack.
	 * @param capacity
	 *            the maximum weight allowed for the knapsack.
	 * @return the maximum profit possible for the given weight
	 */
	public static int pack(final Item[] items, final int 

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0
I have used Python, Natural Language Processing and web scraping technology to do some deep mining of Google's vast warehouses of articles on the web.

Is what I described considered artificial intelligence?

Or, in order to satisfy the requirement of AI must that model also automatically adjust it's algorithms based on the results of the searches? In my case, the adjustments were manual.

Curious.

Thanks.
1
I have a trading system that is about 40% right. That means 4/10 signals generated by it yield in profit and the remaining 6 result in loss. Can I use neural networks/AI/Deep-learning to improve the chances? Can neural networks be used, in this case, to filter-out the bad trades in advance such that the trading system produces 60% good trades?
0
I'm creating an Avl tree to sort information about some countries. I want each node to be a list with 2 parameters being the name of the country the first and the information specific to the country  the second. Is it possible the second parameter of the node to be another avl tree?

Thanks.
0
I have some written material that I need to organize. The material is in separate documents. I would like some (easy, non-complicated) automated method that could parse the documents into some sensible format. Initially, I need a table of contents for a writing project I'm involved in. Can a table of contents be generated from separate documents? Is there a way to cluster/classify the text? Neural Network text analysis seems like overkill. Mind Mapping also seems like a lot of work. Maybe MS Word? I can merge the documents into one document if that would help. Any ideas appreciated and points awarded for workable solutions. Thanks.
0
Here goes the code, and the compiler shows the warning : qmain.c:49:20: error: expected ‘;’, ‘,’ or ‘)’ before ‘.’ token
 void qdelete(int* q.front, int* q.rear)


#include<stdio.h>
#include<stdlib.h>
#define size 50

typedef struct queue
{
int a[size];
int front;
int rear;
}ob;

ob q;

void qdelete(int*, int*); 

void insert ()
{
int ele;

printf("\nEnter the element to be inserted:\t");
scanf("%d", &ele);

if((q.rear+1)%size==q.front)
			// same as this : if((q.front==0)&&(q.rear=size-1)||(q.rear+1==q.front))
{
printf("\nQUEUE IS FULL !!\nNo more elements can be inserted.");
return;
}

else
	{
	if(q.rear==size-1)
		q.rear=0;
	else
		q.rear++;
	}
	q.a[q.rear]= ele;
		
	if(q.front==-1)
		{
		q.front=0;
		printf("%d rear = %d front is the first element of the queue.", q.a[q.rear], q.a[q.front]);
		}
	
	printf("\n%d Inserted",q.a[q.rear]);
}


void qdelete(int* q.front, int* q.rear)
{
if(q.front==-1)
	{
	printf("\nQueue empty");
	return;
	}
	
else
	{
		printf("\nElement output %d", q.a[q.front] );
	
		if(q.front==q.rear)
			{
			q.front=-1;
			q.rear=-1;
			}
		else
		{	
		q.front==(q.front+1)%size;

					/*	same as this: 
					if(q.front==size-1)
							q.front=0;
						else
							q.front++;	*/
		}
		printf("\nDeleted");
	}
}

void display ()
{
int i=q.front, j=q.rear;
printf("\nDISPLAY:\t");

while(i!=j)
{
printf(" %d ", q.a[i++]);
}

printf (" %d", q.a[i]);
printf("\n");
}


void main()
{
int choice;
q.front = -1;
q.rear = -1;

while(1)

	{
	

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0
I am building a backups application in which I want to know the files that have been Added/modified/Renamed/Deleted.
I am trying out the ReadDirectoryChangesW() Windows API. I created two files TestNewFile.xlsx and TestNewTextFile.txt.

I get so many notifications, How can I get a workable result ?
Is there some Algorithm to manage these ?

I use Delphi with SQL Lite catering to all Windows OS

Results while Creating Excel File

waAdded   TestNewFile.xlsx
waRemoved   TestNewFile.xlsx
waAdded   ~$TestNewFile.xlsx
waModified   ~$TestNewFile.xlsx
waModified   ~$TestNewFile.xlsx
waAdded   90A4C000
waModified   90A4C000
waModified   90A4C000
waModified   90A4C000
waModified   90A4C000
waModified   90A4C000
waModified   90A4C000
waRenamedOld   90A4C000
waRenamedNew   TestNewFile.xlsx
waModified   TestNewFile.xlsx

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Results while Creating Notepad File

waAdded   TestNewTextFile.txt
waRemoved   TestNewTextFile.txt
waAdded   TestNewTextFile.txt
waModified   TestNewTextFile.txt
waModified   TestNewTextFile.txt

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Other Results that keep coming on their own or while using Windows Explorer.

waModified   Users\SS Smith\ntuser.dat.LOG1
waModified   Users\SS Smith\NTUSER.DAT
waAdded   Windows\Prefetch\TASKMGR.EXE-5F5F473D.pf
waModified   Windows\Prefetch
waModified   Users\SS Smith\AppData\Local\Microsoft\Windows\UsrClass.dat.LOG1
waModified   Users\SS Smith\AppData\Local\Microsoft\Windows\UsrClass.dat
waModified   Windows\Prefetch\DLLHOST.EXE-5E46FA0D.pf
waModified   Windows\System32\wbem\Repository\OBJECTS.DATA
waModified   Windows\System32\wbem\Repository\INDEX.BTR
waModified   Windows\System32\wbem\Repository\MAPPING2.MAP
waModified   Windows\Prefetch\AVWSC.EXE-327FD431.pf

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0
Survive A High-Traffic Event with Percona
LVL 3
Survive A High-Traffic Event with Percona

Your application or website rely on your database to deliver information about products and services to your customers. You can’t afford to have your database lose performance, lose availability or become unresponsive – even for just a few minutes.

Anyone know of a relatively straightforward algorithm for computing the numbers of ones and zeroes in an arbitrary string such that, we could address the function thus

Number_of_Ones=bitcount(arbitrary_string,1)
Number_of_Zeroes=bitcount(arbitrary_string,0)
0
Assuming a given time for sunrise or sunset at sea level, what adjustment have to be made to those times for a given altitude (i.e. 2400 feet).
0
I'm a little lacking in the statistics area - more like a lot.
I have a list of numbers in excel that I think might be related to a stock price trend.
There are about 2000 + representing each day along with the comparative stock price at that same time.
I also record whether the stock went up or not from the previous day.
I want to know if the Number column is related to the trend column.  It cold be related to the current day, the next day or perhaps days in the future using the number column as the base. The end result would be to say that the

Does anyone have an idea on how I could examine this - whether in excel or in some other method (i'm good in vba, very basic python)?
Sample.xlsx
0
I have the need of being able to generate random directed, cyclic graphs, but according to some constraints.

I would like to input a few parameters/constraints, and obtain a random directed graph that meets those constraints.  Every graph has a terminal node.  Some examples of constraints are:

1) min/max number of child nodes per node
2) length of shortest path from input to a terminal node
3) max number of nodes in graph
4) (possibly) max length of longest path

I don't know much about graph theory, but are there any algorithms or libraries that can generate random graphs similar to this?

Thanks!
0
Hello,

Could you please help me to resolve the following task:
In the text file I have the matrix of connections between points together with the weights for each pair, for instance:
A, B, 10
A, C, 15
B, D, 11
D, C, 12
E, A, 14

Now, I need to convert these data into the graph matrix with zeroes on diagonal (A,A=0, B,B=0, etc.) and x stands for no weight for pair:
[[0, 10, 15, x, 14],
 [10, 0, x, 11, x],
 [15, x, 0, 12, x],
 [x, 11, 12, 0, x],
 [14, x, x, x, 0]]

I need to do that in c++ but I believe this is rather matter of an algorithm.

Thanks in advance
Mike
0
If I have conversion rate from USD to GBP how can I get the rate to reverse it so that I can covert from GBP to USD?
0

Algorithms

An algorithm is a self-contained step-by-step set of operations to be performed. Algorithms exist that perform calculation, data processing, and automated reasoning. Starting from an initial state and initial input (perhaps empty), the instructions describe a computation that, when executed, proceeds through a finite number of well-defined successive states, eventually producing "output" and terminating at a final ending state. The transition from one state to the next is not necessarily deterministic; some algorithms, known as randomized algorithms, incorporate random input.