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  • Fastest possible summing numbers up to N

    - by dada
    Okay so i need really FAST algorithm or code in C if you have any it would be nice. The task is to sum all numbers from 1 to N for a given number N (it can be negative number too), so i did the usual way (you know just summing with loop from 1 to N) but it's not fast enough - i need something faster, i guess that i need the fastest possible way to do this. If anyone could help me, please do. Thanks.

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  • Subset Problem -- Any Materials?

    - by bobber205
    Yes this is a homework/lab assignment. I am interesting in coming up with/finding an algorithm (I can comprehend :P) for using "backtracking" to solve the subset sum problem. Anyone have some helpful resources? I've spent the last hour or so Googling with not much like finding something I think I could actually use. xD Thanks SO!

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  • Getting the submatrix with maximum sum?

    - by guirgis
    With the help of the Algorithmist and Larry and a modification of Kadane's Algorithm, here is my solution: int dim = matrix.length; //computing the vertical prefix sum for columns int[][] ps = new int[dim][dim]; for (int i = 0; i < dim; i++) { for (int j = 0; j < dim; j++) { if (j == 0) { ps[j][i] = matrix[j][i]; } else { ps[j][i] = matrix[j][i] + ps[j - 1][i]; } } } int maxSoFar = 0; int min , subMatrix; //iterate over the possible combinations applying Kadane's Alg. //int toplefti =0, topleftj=0, bottomrighti=0, bottomrightj=0; for (int i = 0; i < dim; i++) { for (int j = i; j < dim; j++) { min = 0; subMatrix = 0; for (int k = 0; k < dim; k++) { if (i == 0) { subMatrix += ps[j][k]; } else { subMatrix += ps[j][k] - ps[i-1][k]; } if(subMatrix < min){ min = subMatrix; } if((subMatrix - min) > maxSoFar){ maxSoFar = subMatrix - min; } } } } The only problem left is to determine the submatrix elements, i mean the top left and the bottom right corners. I managed to do this in one dimensional case. Any suggestions?

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  • C#: Sum of even fibonacci numbers

    - by user300484
    Hello you all! im developping an application that will find the sum of all even terms of the fibonacci sequence. The last term of this sequence is 4,000,000 . There is something wrong in my code but I cannot find the problem since it makes sense to me. Can you please help me? using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { long[] arr = new long [1000000] ; long i= 2; arr[i-2]=1; arr[i-1]=2; long n= arr[i]; long s=0; for (i=2 ; n <= 4000000; i++) { arr[i] = arr[(i - 1)] + arr[(i - 2)]; } for (long f = 0; f <= arr.Length - 1; f++) { if (arr[f] % 2 == 0) s += arr[f]; } Console.Write(s); Console.Read(); } } }

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  • NSOutlineView/NSTreeController - calculate sum of column

    - by matei
    I have a NSOutlineView bound to a NSTreeController. My data items are a custom class , let's call them "Row", and suppose a Row contains a "name" and a numeric field called "number" . All these "Rows" are found in let's say a "RowContainer" which has a "rows" mutable array holding the parent (level 0) rows. Each row also has a "children" NSMutableArray member which holds it's children. I have this working, and I want to display under the outlineview a textfield with the sum of all the "number" values of the rows. I bound this textfield to a "total" property of the "RowContainer". Now the problem is how or from where to trigger the recalculation of the "total" property, since this involves a recursive walk on the tree of rows, and I always get a "Collection was mutated while being enumerated" error. I've tried making a method "recalculateTotal", and calling it from the "setNumber" method of the "Row" class , but same error occurs. If I put the recalculation logic in the "total" getter, I can't trigger it to do the math. I'm sure the solution is simple but I can't see it

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  • Removing an array dimension where the elements sum to zero

    - by James
    Hi, I am assigning a 3D array, which contains some information for a number of different loadcases. Each row in the array defines a particular loadcase (of which there are 3) and I would like to remove the loadcase (i.e. the row) if ALL the elements of the row (in 3D) are equal to zero. The code I have at the moment is: Array = zeros(3,5) % Initialise array Numloadcases = 3; Array(:,:,1) = [10 10 10 10 10; 0 0 0 0 0; 0 0 0 0 0;]; % Expand to a 3D array Array(:,:,2) = [10 10 10 10 10; 0 0 0 0 0; 0 0 0 0 0;]; Array(:,:,3) = [10 10 10 10 10; 0 0 0 0 0; 0 0 20 0 0;]; Array(:,:,4) = [10 10 10 10 10; 0 0 0 0 0; 0 0 20 0 0;]; % I.e. the second row should be removed. for i = 1:Numloadcases if sum(Array(i,:,:)) == 0; Array(i,:,:) = [] end end At the moment, the for loop I have to remove the rows causes an indexing error, as the size of the array changes in the loop. Can anyone see a work around for this? Thanks

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  • Simple encryption - Sum of Hashes in C

    - by Dogbert
    I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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  • Sum of even fibonacci numbers

    - by user300484
    This is a Project Euler problem. If you don't want to see candidate solutions don't look here. Hello you all! im developping an application that will find the sum of all even terms of the fibonacci sequence. The last term of this sequence is 4,000,000 . There is something wrong in my code but I cannot find the problem since it makes sense to me. Can you please help me? using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { long[] arr = new long [1000000] ; long i= 2; arr[i-2]=1; arr[i-1]=2; long n= arr[i]; long s=0; for (i=2 ; n <= 4000000; i++) { arr[i] = arr[(i - 1)] + arr[(i - 2)]; } for (long f = 0; f <= arr.Length - 1; f++) { if (arr[f] % 2 == 0) s += arr[f]; } Console.Write(s); Console.Read(); } } }

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  • Reporting Services Sum of Inner Group in Outer Group

    - by Spoonybard
    I have a report in Reporting Services 2008 using ASP.net 3.5 and SQL Server 2008. The report has 2 groupings and a detail row. This is the current format: Outer Group Inner Group Detail Row The Detail Row represents an item on a receipt and a receipt can have multiple items. Each receipt was paid with a certain payment method. So the Outer Group is grouped by payment type, the Inner Group is grouped by the receipt's ID, and the Detail Row is each item for the given receipt. My raw data result set has two important columns: The Amount Received and the Amount Applied. The Amount Received is how much money in total was collected for all the items on the receipt. The Amount Applied is how much money each item got from the total Amount Received. Sample Result Set: ReceiptID Item ItemID AmountReceived AmountApplied Payment Method ------------------------------------------------------------------------------------------ 1 Book 1 $200.00 $40.00 Cash 1 CD 2 $200.00 $20.00 Cash 1 Software 3 $200.00 $100.00 Cash 1 Backpack 4 $200.00 $40.00 Cash The Inner Group displays the AmountReceived correctly as $200. However, the Outer Group displays the AmountReceived as $800, because I believe that it is going off each detail row which in this case is a count of 4 items. What I want is to see in the Outer Group that the Amount Received is $200. I tried restricting the scope in my SUM function to be the Inner Group, but I get the error "The scope parameter must be set to a string constant that is equal to either the name of a containing group, the name of a containing data region, or the name of a dataset." Does anyone have any suggestions on how to solve this issue? Thanks.

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  • Is there a version of the Arial or Tahoma font with monospaced digits and spaces?

    - by rossmcm
    The digits in the Arial font supplied with Windows are monospaced, in that they each take up the same horizontal space, but they seem to have neglected to provide a "monospaced" version of the space character. This means that you can't format a column of digits right-justified in (say) 12 spaces and have the right-hand edge be aligned. For example: 1 12 123 1234 12345 1234567 12345678 123456789 1234567890 works because the font used for code examples has spaces the same width as digits. This however doesn't work if the same text is displayed in Arial (I can't demonstrate because I can't figure out how to defeat SU's reformatting at the moment!). It just so happens that with Tahoma 8 point you can cheat because a space is exactly half the number of pixels as a digit, but that is messy and very specific.

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  • Python: Improving long cumulative sum

    - by Bo102010
    I have a program that operates on a large set of experimental data. The data is stored as a list of objects that are instances of a class with the following attributes: time_point - the time of the sample cluster - the name of the cluster of nodes from which the sample was taken code - the name of the node from which the sample was taken qty1 = the value of the sample for the first quantity qty2 = the value of the sample for the second quantity I need to derive some values from the data set, grouped in three ways - once for the sample as a whole, once for each cluster of nodes, and once for each node. The values I need to derive depend on the (time sorted) cumulative sums of qty1 and qty2: the maximum value of the element-wise sum of the cumulative sums of qty1 and qty2, the time point at which that maximum value occurred, and the values of qty1 and qty2 at that time point. I came up with the following solution: dataset.sort(key=operator.attrgetter('time_point')) # For the whole set sys_qty1 = 0 sys_qty2 = 0 sys_combo = 0 sys_max = 0 # For the cluster grouping cluster_qty1 = defaultdict(int) cluster_qty2 = defaultdict(int) cluster_combo = defaultdict(int) cluster_max = defaultdict(int) cluster_peak = defaultdict(int) # For the node grouping node_qty1 = defaultdict(int) node_qty2 = defaultdict(int) node_combo = defaultdict(int) node_max = defaultdict(int) node_peak = defaultdict(int) for t in dataset: # For the whole system ###################################################### sys_qty1 += t.qty1 sys_qty2 += t.qty2 sys_combo = sys_qty1 + sys_qty2 if sys_combo > sys_max: sys_max = sys_combo # The Peak class is to record the time point and the cumulative quantities system_peak = Peak(time_point=t.time_point, qty1=sys_qty1, qty2=sys_qty2) # For the cluster grouping ################################################## cluster_qty1[t.cluster] += t.qty1 cluster_qty2[t.cluster] += t.qty2 cluster_combo[t.cluster] = cluster_qty1[t.cluster] + cluster_qty2[t.cluster] if cluster_combo[t.cluster] > cluster_max[t.cluster]: cluster_max[t.cluster] = cluster_combo[t.cluster] cluster_peak[t.cluster] = Peak(time_point=t.time_point, qty1=cluster_qty1[t.cluster], qty2=cluster_qty2[t.cluster]) # For the node grouping ##################################################### node_qty1[t.node] += t.qty1 node_qty2[t.node] += t.qty2 node_combo[t.node] = node_qty1[t.node] + node_qty2[t.node] if node_combo[t.node] > node_max[t.node]: node_max[t.node] = node_combo[t.node] node_peak[t.node] = Peak(time_point=t.time_point, qty1=node_qty1[t.node], qty2=node_qty2[t.node]) This produces the correct output, but I'm wondering if it can be made more readable/Pythonic, and/or faster/more scalable. The above is attractive in that it only loops through the (large) dataset once, but unattractive in that I've essentially copied/pasted three copies of the same algorithm. To avoid the copy/paste issues of the above, I tried this also: def find_peaks(level, dataset): def grouping(object, attr_name): if attr_name == 'system': return attr_name else: return object.__dict__[attrname] cuml_qty1 = defaultdict(int) cuml_qty2 = defaultdict(int) cuml_combo = defaultdict(int) level_max = defaultdict(int) level_peak = defaultdict(int) for t in dataset: cuml_qty1[grouping(t, level)] += t.qty1 cuml_qty2[grouping(t, level)] += t.qty2 cuml_combo[grouping(t, level)] = (cuml_qty1[grouping(t, level)] + cuml_qty2[grouping(t, level)]) if cuml_combo[grouping(t, level)] > level_max[grouping(t, level)]: level_max[grouping(t, level)] = cuml_combo[grouping(t, level)] level_peak[grouping(t, level)] = Peak(time_point=t.time_point, qty1=node_qty1[grouping(t, level)], qty2=node_qty2[grouping(t, level)]) return level_peak system_peak = find_peaks('system', dataset) cluster_peak = find_peaks('cluster', dataset) node_peak = find_peaks('node', dataset) For the (non-grouped) system-level calculations, I also came up with this, which is pretty: dataset.sort(key=operator.attrgetter('time_point')) def cuml_sum(seq): rseq = [] t = 0 for i in seq: t += i rseq.append(t) return rseq time_get = operator.attrgetter('time_point') q1_get = operator.attrgetter('qty1') q2_get = operator.attrgetter('qty2') timeline = [time_get(t) for t in dataset] cuml_qty1 = cuml_sum([q1_get(t) for t in dataset]) cuml_qty2 = cuml_sum([q2_get(t) for t in dataset]) cuml_combo = [q1 + q2 for q1, q2 in zip(cuml_qty1, cuml_qty2)] combo_max = max(cuml_combo) time_max = timeline.index(combo_max) q1_at_max = cuml_qty1.index(time_max) q2_at_max = cuml_qty2.index(time_max) However, despite this version's cool use of list comprehensions and zip(), it loops through the dataset three times just for the system-level calculations, and I can't think of a good way to do the cluster-level and node-level calaculations without doing something slow like: timeline = defaultdict(int) cuml_qty1 = defaultdict(int) #...etc. for c in cluster_list: timeline[c] = [time_get(t) for t in dataset if t.cluster == c] cuml_qty1[c] = [q1_get(t) for t in dataset if t.cluster == c] #...etc. Does anyone here at Stack Overflow have suggestions for improvements? The first snippet above runs well for my initial dataset (on the order of a million records), but later datasets will have more records and clusters/nodes, so scalability is a concern. This is my first non-trivial use of Python, and I want to make sure I'm taking proper advantage of the language (this is replacing a very convoluted set of SQL queries, and earlier versions of the Python version were essentially very ineffecient straight transalations of what that did). I don't normally do much programming, so I may be missing something elementary. Many thanks!

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  • Sum multi dimensional array based on a key in php

    - by user1328178
    I have mutiple arrays say for now 2, first array has Cities(Mumbai, Pune. Bangalore, Hyderabad) And 2nd array has Mumbia nad Hyderabd. I want to sum up the values based on the Key. Array ( [Mumbai] = Array ( [ga:pageviews] = 1 [ga:visits] = 1 [ga:newVisits] = 1 [ga:pageviewsPerVisit] = 1 [ga:entranceBounceRate] = 1 [ga:avgTimeOnSite] = 1 [ga:timeOnSite] = 1 [ga:bounces] = 1 ) [Pune] => Array ( [ga:pageviews] => 2 [ga:visits] => 2 [ga:newVisits] => 2 [ga:pageviewsPerVisit] => 2 [ga:entranceBounceRate] => 2 [ga:avgTimeOnSite] => 2 [ga:timeOnSite] => 2 [ga:bounces] => 2 ) [Bangalore] => Array ( [ga:pageviews] => 3 [ga:visits] => 3 [ga:newVisits] => 3 [ga:pageviewsPerVisit] => 3 [ga:entranceBounceRate] => 3 [ga:avgTimeOnSite] => 3 [ga:timeOnSite] => 3 [ga:bounces] => 3 ) [Hyderabad] => Array ( [ga:pageviews] => 4 [ga:visits] => 4 [ga:newVisits] => 4 [ga:pageviewsPerVisit] => 4 [ga:entranceBounceRate] => 4 [ga:avgTimeOnSite] => 4 [ga:timeOnSite] => 4 [ga:bounces] => 4 ) ) 2nd Array: Array ( [Mumbai] = Array ( [ga:pageviews] = 5 [ga:visits] = 5 [ga:newVisits] = 5 [ga:pageviewsPerVisit] = 5 [ga:entranceBounceRate] = 5 [ga:avgTimeOnSite] = 5 [ga:timeOnSite] = 5 [ga:bounces] = 5 ) [Hyderabad] => Array ( [ga:pageviews] => 2 [ga:visits] => 2 [ga:newVisits] => 2 [ga:pageviewsPerVisit] => 2 [ga:entranceBounceRate] => 2 [ga:avgTimeOnSite] => 2 [ga:timeOnSite] => 2 [ga:bounces] => 2 ) ) I want the result as: Array ( [Mumbai] = Array ( [ga:pageviews] = 6 [ga:visits] = 6 [ga:newVisits] = 6 [ga:pageviewsPerVisit] = 6 [ga:entranceBounceRate] = 6 [ga:avgTimeOnSite] = 6 [ga:timeOnSite] = 6 [ga:bounces] = 6 ) [Pune] => Array ( [ga:pageviews] => 2 [ga:visits] => 2 [ga:newVisits] => 2 [ga:pageviewsPerVisit] => 2 [ga:entranceBounceRate] => 2 [ga:avgTimeOnSite] => 2 [ga:timeOnSite] => 2 [ga:bounces] => 2 ) [Bangalore] => Array ( [ga:pageviews] => 3 [ga:visits] => 3 [ga:newVisits] => 3 [ga:pageviewsPerVisit] => 3 [ga:entranceBounceRate] => 3 [ga:avgTimeOnSite] => 3 [ga:timeOnSite] => 3 [ga:bounces] => 3 ) [Hyderabad] => Array ( [ga:pageviews] => 6 [ga:visits] => 6 [ga:newVisits] => 6 [ga:pageviewsPerVisit] => 6 [ga:entranceBounceRate] => 6 [ga:avgTimeOnSite] => 6 [ga:timeOnSite] => 6 [ga:bounces] => 6 ) ) Thanks for your help.... Ruth.

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  • Add up values from a text file

    - by Stanley
    Hi Guys I have a text file that contains Amounts at Substring (34, 47) of each line. I need to sum Up all the Values to the End of the File. I have this code that I had started to build but I do not know how to proceed from here: public class Addup { /** * @param args the command line arguments */ public static void main(String[] args) throws FileNotFoundException, IOException { // TODO code application logic here FileInputStream fs = new FileInputStream("C:/Analysis/RL004.TXT"); BufferedReader br = new BufferedReader(new InputStreamReader(fs)); String line; while((line = br.readLine()) != null){ String num = line.substring(34, 47); double i = Double.parseDouble(num); System.out.println(i); } } } The output is like this: 1.44576457E4 2.33434354E6 4.56875685E3 The Amount is in two decimal Places and I need the result also in the Two decimal Places. What Is the Best way to achieve this?

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  • How to round a number to n decimal places in Java

    - by Alex Spurling
    What I'd like is a method to convert a double to a string which rounds using the half-up method. I.e. if the decimal to be rounded is a 5, it always rounds up the previous number. This is the standard method of rounding most people expect in most situations. I also would like only significant digits to be displayed. That is there should not be any trailing zeroes. I know one method of doing this is to use the String.format method: String.format("%.5g%n", 0.912385); returns: 0.91239 which is great, however it always displays numbers with 5 decimal places even if they are not significant: String.format("%.5g%n", 0.912300); returns: 0.91230 Another method is to use the DecimalFormatter: DecimalFormat df = new DecimalFormat("#.#####"); df.format(0.912385); returns: 0.91238 However as you can see this uses half-even rounding. That is it will round down if the previous digit is even. What I'd like is this: 0.912385 -> 0.91239 0.912300 -> 0.9123 What is the best way to achieve this in Java?

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  • Define a positive number to be isolated if none of the digits in its square are in its cube [closed]

    - by proglaxmi
    Define a positive number to be isolated if none of the digits in its square are in its cube. For example 163 is n isolated number because 69*69 = 26569 and 69*69*69 = 4330747 and the square does not contain any of the digits 0, 3, 4 and 7 which are the digits used in the cube. On the other hand 162 is not an isolated number because 162*162=26244 and 162*162*162 = 4251528 and the digits 2 and 4 which appear in the square are also in the cube. Write a function named isIsolated that returns 1 if its argument is an isolated number, it returns 0 if its not an isolated number and it returns -1 if it cannot determine whether it is isolated or not (see the note below). The function signature is: int isIsolated(long n) Note that the type of the input parameter is long. The maximum positive number that can be represented as a long is 63 bits long. This allows us to test numbers up to 2,097,151 because the cube of 2,097,151 can be represented as a long. However, the cube of 2,097,152 requires more than 63 bits to represent it and hence cannot be computed without extra effort. Therefore, your function should test if n is larger than 2,097,151 and return -1 if it is. If n is less than 1 your function should also return -1. Hint: n % 10 is the rightmost digit of n, n = n/10 shifts the digits of n one place to the right. The first 10 isolated numbers are N n*n n*n*n 2 4 8 3 9 27 8 64 512 9 81 729 14 196 2744 24 576 13824 28 784 21952 34 1156 39304 58 3364 195112 63 3969 250047

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  • Add two hexBinarys with XPATH 1.0

    - by fielding
    Hi, my xml document looks somewhat like that (Values are both xsl:hexBinary): <Offsets> <Offset> <Name>ErrorOffset</Name> <Value>DD</Value> </Offset> <Offset> <Name>OtherOffset</Name> <Value>FF</Value> </Offset> </Offsets> <Value> <Name>Error1</Name> <Code>01</Code> </Value> <Value> <Name>Error2</Name> <Code>02</Code> <Offset>ErrorOffset</Offset> </Value> now i want to transform this to a new xml file: <Value> <Name>Error1</Name> <Code>01</Code> </Value> <Value> <Name>Error2</Name> <Code>DF</Code> </Value> All that should happen is adding <Offset> to the basic <Value>. But plain + returns NaN and sum() expects only one parameter. XSLT and XPATH are quite nice, but it goes on my nerves that easy operations like adding two hex values just dont work as easy as it should.

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  • Is your Credit Card Number valid?

    - by Rekha
    The credit card numbers may look like some random unique 16 digits number but those digits inform more than what we think it could be. The first digit of the card is the Major Industry Identifier: 1 and 2 -  Airlines 3  – Travel and Entertainment 4 and 5 -  Banking and Financial 6 – Merchandizing and Banking 7 – Petroleum 8 – Telecommunications 9 – National assignment The first 6 digits represent the Issuer Identification Number: Visa – 4xxxxx Master Card – 51xxxx & 55xxxx The 7th and following digits, excluding the last digit, are the person’s account number which leads to trillion possible combinations if the maximum of 12 digits is used. Many cards only use 9 digits. The final digit is the checksum or check digit. It is used to validate the card number using Luhn algorithm. How To Validate Credit Card Number? Take any credit card number, for example 5588 3201 2345 6789. Step 1: Double every other digit from the right: 5*2      8*2      3*2      0*2      2*2      4*2      6*2      8*2 ————————————————————————- 10        16        6          0          4          8      12        16 Step 2: Add these new digits to undoubled digits. All double digit numbers are added as a sum of their digits, so 16 becomes 1+6 = 7: Undoubled digits:       5          8          2          1          3          5          7          9 Doubled Digits:          10       16         6          0          4          8         12         16 Sum:  5+1+0+8+1+6+2+6+1+0+3+4+5+8+7+1+2+9+1+6 = 76 If the final sum is divisible by 10, then the Credit Card number is valid, if not, the number is invalid or fake!!! Hence the example is a fake number? via mint  cc and image credit This article titled,Is your Credit Card Number valid?, was originally published at Tech Dreams. Grab our rss feed or fan us on Facebook to get updates from us.

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  • Question regarding ip checksum code

    - by looktt
    unsigned short /* this function generates header checksums */ csum (unsigned short *buf, int nwords) { unsigned long sum; for (sum = 0; nwords > 0; nwords--) // add words(16bits) together sum += *buf++; sum = (sum >> 16) + (sum & 0xffff); //add carry over sum += (sum >> 16); //what does this step do??? add possible left-over //byte? But isn't it already added in the loop (if //any)? return ((unsigned short) ~sum); } I assume nwords in the number of 16bits word, not 8bits byte (if there are odd byte, nword is rounded to next large), is it correct? The line sum = (sum 16) + (sum & 0xffff) is to add carry over to make 16bit complement sum += (sum 16); What's the purpose of this step? Add left-over byte? How? Thanks!

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  • stored procedure issue, has to do with my where clause and if statement

    - by MyHeadHurts
    right now my stored procedure is returning 2 different result sets one for @booked and the other for @booked1 if you look closely my query is doing the same thing for each @booked and @booked but one is for a user selected year and the other for the current year. I don't want two different result sets, i want to join the selected year and the current year side by side by SDESCR(which is a column that they have in common) another hurdle i am facing is i am use @mode to decide whether the user wants netsales, sales... so on. I know i need sometype of join but, it isnt working because i have a where statement that says where dyyyy= @yeartoget which won't allow the current year data to work ALTER PROCEDURE [dbo].[test1] @mode varchar(20), @YearToGet int AS SET NOCOUNT ON Declare @Booked Int Set @Booked = CONVERT(int,DateAdd(year, @YearToGet - Year(getdate() + 1), DateAdd(day, DateDiff(day, 1, getdate()), 1) ) ) Declare @Booked1 Int Set @Booked1 = CONVERT(int,DateAdd(year, (year( getdate() )) - Year(getdate() + 1), DateAdd(day, DateDiff(day, 1, getdate()), 1) ) ) If @mode = 'Sales' Select Division, SDESCR, DYYYY, Sum(Case When Booked <= @Booked Then NetAmount End) ASofNetSales, SUM(NetAmount) AS YENetSales, Sum(Case When Booked <= @Booked Then PARTY End) AS ASofPAX, SUM(PARTY) AS YEPAX From dbo.B101BookingsDetails Where DYYYY = @YearToGet Group By SDESCR, DYYYY, Division Order By Division, SDESCR, DYYYY else if @mode = 'netsales' Select Division, SDESCR, DYYYY, Sum(Case When Booked <= @Booked Then NetAmount End) ASofNetSales, SUM(NetAmount) AS YENetSales, Sum(Case When Booked <= @Booked Then PARTY End) AS ASofPAX, SUM(PARTY) AS YEPAX From dbo.B101BookingsDetails Where DYYYY = @YearToGet Group By SDESCR, DYYYY, Division Order By Division, SDESCR, DYYYY If @mode = 'Sales' Select Division, SDESCR, DYYYY, Sum(Case When Booked <= @Booked1 Then NetAmount End) currentNetSales, Sum(Case When Booked <= @Booked1 Then PARTY End) AS currentPAX From dbo.B101BookingsDetails Where DYYYY = (year( getdate() )) Group By SDESCR, DYYYY, Division Order By Division, SDESCR, DYYYY else if @mode = 'netsales' Select Division, SDESCR, DYYYY, Sum(Case When Booked <= @Booked1 Then NetAmount End) currentNetSales, Sum(Case When Booked <= @Booked1 Then PARTY End) AS currentPAX From dbo.B101BookingsDetails Where DYYYY = (year( getdate() )) Group By SDESCR, DYYYY, Division Order By Division, SDESCR, DYYYY Else if @mode = 'Inssales' Select Division, SDESCR, DYYYY, Sum(Case When Booked <= @Booked1 Then InsAmount End) currentInsSales, Sum(Case When Booked <= @Booked1 Then PARTY End) AS currentPAX From dbo.B101BookingsDetails Where DYYYY = (year( getdate() )) Group By SDESCR, DYYYY, Division Order By Division, SDESCR, DYYYY

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  • Incorrect value for sum of two NSIntegers

    - by Antonio
    Hi everybody: I'm sure I'm missing something and the answer is very simple, but I can't seem to understand why this is happening. I'm trying to make an average of dates: NSInteger runningSum =0; NSInteger count=0; for (EventoData *event in self.events) { NSDate *dateFromString = [[NSDate alloc] init]; if (event.date != nil) { dateFromString = [dateFormatter dateFromString:event.date]; runningSum += (NSInteger)[dateFromString timeIntervalSince1970]; count += 1; } } if (count>0) { NSLog(@"average is: %@",[NSDate dateWithTimeIntervalSince1970:(NSInteger)((CGFloat)runningAverage/count)]); } Everything seems to work OK, except for runningSum += (NSInteger)[dateFromString timeIntervalSince1970], which gives an incorrect result. If I put a breakpoint when taking the average of two equal dates (2009-10-10, for example, which is a timeInterval of 1255125600), runningSum is -1784716096, instead of the expected 2510251200. I've tried using NSNumber and I get the same result. Can anybody point me in the right direction? Thanks! Antonio

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  • Excel VBAa: Sum invoice by client id with copying result to new worksheet

    - by Melkior
    Hi, i have strange problem doing reporting: i have numerous clients with different issued invoices. Problem comes to the point when there are invoices in minus and plus: Column A consists of client unique IDs, Column B invoice number, column C invoice amount A | B | C 0010019991 | 1800149471 | 162.00 0010019991 | 1800136388 | 162.00 0010019991 | 1600008004 | -36.00 0010021791 | 1800132148 | 162.00 0010021791 | 1800145436 | 162.00 0010021791 | 1600007737 | -12.00 0014066147 | 1800119068 | 1,684.80 0014066147 | 1800123702 | 1,684.80 0014066147 | 1600007980 | -1,300.80 0014066147 | 1600007719 | -1,286.40 I need to remove rows with negative invoices in a way that amount is summed with invoices which are not with negative amount. So that final result would look like: A | B | C 0010019991 | 1800149471 | 126.00 0010019991 | 1800136388 | 162.00 0010021791 | 1800132148 | 150.00 0010021791 | 1800145436 | 162.00 0014066147 | 1800123702 | 782.40

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  • Create a Cumulative Sum Column in MySQL

    - by Kirk
    I have a table that looks like this: id count 1 100 2 50 3 10 I want to add a new column called cumulative_sum, so the table would look like this: id count cumulative_sum 1 100 100 2 50 150 3 10 160 Is there a MySQL update statement that can do this easily? What's the best way to accomplish this?

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