Develop Reference

How to sort an array based on specific index [duplicate]

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How to sort an array containing class objects by a property value of a class instance? [duplicate]
(2 answers)
Closed 7 years ago.
I Have an array like below code :
struct Book_Struct
{
public string Title;
public string Auther;
public int Date;
public int ID;
}
static void Print(Book_Struct[] a, int b)
{
for (int i = 0; i < b; i++)
{
Console.WriteLine(" Name of Book " + (i + 1) + " is : " + "\" " + a[i].Title + " \"");
Console.WriteLine("Auther of Book " + (i + 1) + " is : " + "\" " + a[i].Auther + " \"");
Console.WriteLine(" Date of Book " + (i + 1) + " is : " + "\" " + a[i].Date + " \"");
Console.WriteLine(" ID of Book " + (i + 1) + " is : " + "\" " + a[i].ID + " \"");
Console.WriteLine("\n---------------------------------\n");
}
}
I want sort this array based on for example Title of Books. How do i it?

You could use Array.Sort:
Array.Sort(a, (b1, b2) => b1.Title.CompareTo(b2.Title));
or LINQ:
a = a.OrderBy(book => book.Title).ToArray();
The latter needs to recreate the array.
As an aside, use a class instead of a mutable struct.

Use LINQ's OrderBy to sort the array:
a = a.OrderBy(x => x.Title).ToArray();
Reference

Extracting common terms with MathNet Symbolics

I'm using MathNet Symbolics to handle the symbolic algebra portion of a program I'm working on. The general use is create a pair of symbolic formulas, and then divide those two formulas. This works quite well most of the time. However, sometimes, it does not want to do more complex simplification. For example:
(512*r*t*w + 2048*r*t^2*w)
-----------------------------------------------------------------------
(512*r*t*w + 512*r^2*t*w + 3072*r*t^2*w + 3072*r^2*t^2*w + 1024*r*t^3*w)
With some work, I've been able to have it eliminate w from the equation, as it is in all terms top and bottom:
(512*r*t + 2048*r*t^2)
--------------------------------------------------------------
(512*r*t + 512*r^2*t + 3072*r*t^2 + 3072*r^2*t^2 + 1024*r*t^3)
However, I cannot figure out how to make it find common terms:
(512*r*t)*(1 + 4*t)
--------------------------------------
(512*r*t)(1 + r + 6*t + 6*r*t + 2*t^2)
And eliminate these terms:
(1 + 4*t)
-----------------------------
(1 + r + 6*t + 6*r*t + 2*t^2)
I've been using Wolfram Alpha as my gold standard for checking my work. The code from LinqPad I've been working on most of the afternoon, that gets my the elimination of w:
var h1 = MathNet.Symbolics.Infix.ParseOrUndefined("(1/8)*r*t*w + (1/2)*r*t^2*w");
var h2 = MathNet.Symbolics.Infix.ParseOrUndefined("(1/8)*r*t*w + (1/8)*r^2*t*w + (3/4)*r*t^2*w + (3/4)*r^2*t^2*w + (1/4)*r*t^3*w");
Infix.Print(Rational.Expand(h1/h2)).Dump(); //Prints (512*r*t*w + 2048*r*t^2*w)/(512*r*t*w + 512*r^2*t*w + 3072*r*t^2*w + 3072*r^2*t^2*w + 1024*r*t^3*w)
var tot = Rational.Expand(h1 / h2);
var simplified = true;
do
{
simplified=false;
foreach (var v in Rational.Variables(tot))
{
var result = Polynomial.Divide(v, h1, h2);
if (!result.Item1.Equals(MathNet.Symbolics.Expression.Zero))
{
simplified = true;
tot = result.Item1;
break;
}
}
}while(simplified);
tot = Rational.Expand(tot);
Infix.Print(tot).Dump(); //Prints (512*r*t + 2048*r*t^2)/(512*r*t + 512*r^2*t + 3072*r*t^2 + 3072*r^2*t^2 + 1024*r*t^3)
Can someone give me pointers to how to proceed with MathNet? I've tried various combinations of functions from Rational and Polynomial, and have not been able to move past this point.

I've just published a new Math.NET Symbolics release v0.6.0 which includes a new Rational.Reduce routine that removes such common simple factors (also executed as part of Rational.Expand):
var h1 = Infix.ParseOrThrow("(1/8)*r*t*w + (1/2)*r*t^2*w");
var h2 = Infix.ParseOrThrow("(1/8)*r*t*w + (1/8)*r^2*t*w + (3/4)*r*t^2*w + (3/4)*r^2*t^2*w + (1/4)*r*t^3*w");
var q1 = h1/h2;
Infix.Print(q1);
// returns: ((1/8)*r*t*w + (1/2)*r*t^2*w)/((1/8)*r*t*w + (1/8)*r^2*t*w + (3/4)*r*t^2*w + (3/4)*r^2*t^2*w + (1/4)*r*t^3*w)
var q2 = Rational.Expand(q1);
Infix.Print(q2);
// returns: (1 + 4*t)/(1 + r + 6*t + 6*r*t + 2*t^2)
Unfortunately quite a few of the univariate polynomial and rational routines like the new square-free factorization do not have a multivariate counterpart yet. Univariate routines expect one symbol parameter, while multivariate ones expect a symbol set.

c# Fractional Calculator - Working out Box?

I'm working on a project where I need to develop a fractional calculator.
I want to add something extra to it, such as having a working out box that displays how the user got their answer.
For example, say I enter 1 1/2 + 1 1/2 into the calculate and press "Calculate", it would then display the answer and how it got the answer such as:
= 3/2 + 3/2
= ((3 × 2) + (3 × 2)) / (2 × 2)
= (6 + 6) / 4
= 12/4
= 3/1
= 3
Here is my basic, crappy looking, program: http://gyazo.com/1dc27b531873c48cdb198baa40b3af9a
I want it to display the working out in the 'Calculations' box below.
How am I able to do this?

Your question is missing some details, so here is a simple answer to begin with.
(I guess your GUI is winforms, and you have a trigger for the calculate OnClick)
To add text into your "Calculations" textbox the code you need is (for your example):
private void calculateButton_Click(object sender, EventArgs e)
{
int common_den = denumerator1*denumerator2;
int new_enumerator1 = enumerator1 * denumerator2;
int new_enumerator2 = enumerator2 * denumerator1;
string myCalculations = " = " + enumerator1.ToString() + "/" + denumerator1.ToString() + " + " + enumerator2.ToString() + "/" + denumerator2.ToString();
string myCalculations += " = " + new_enumerator1.ToString() + "/" + common_den.ToString() + " + " + new_enumerator2.ToString() + "/" + common_den.ToString();
string myCalculations += " = " + (new_enumerator1 + new_enumerator2).ToString() + "/" + common_den.ToString();
calculationsTextBox.Text = myCalculations;
}
If you are looking for the code that will build the calculation string - you need to ask for it explicitly

Count the number of rows in each column

How can I count number of rows in specified column in a Excel sheet?
For example I have 2 columns in a spreadsheet:
A B
--- -----
abc hi
fff hello
ccc hi
hello
The result should look like:
count of A column is 3
count of B column is 4
How can I do this using Microsoft Interop?

The approach suggested by Doug Glancy is accurate and simple to be implemented. You can write the function and retrieve the value from a cell not seenable by the user (ZZ1000, for example). The code is straightforward:
Range notUsed = curSheet.get_Range("ZZ1000", "ZZ1000");
string targetCol = "A";
notUsed.Value2 = "=COUNTA(" + targetCol + ":" + targetCol + ")";
int totRows = Convert.ToInt32(notUsed.Value2);
notUsed.Value2 = "";
UPDATE ---
From your example I understood that you were looking for the total number of non-empty cells, what COUNTA delivers. But, apparently, this is not the case: you want the row number of the last non-empty cell; that is, by using a more descriptive example:
C
---
abc
fff
ccc
hello
You don't want to count the number of non-empty cells (4 in this case; what COUNTA delivers), but the position of "hello", that is, 5.
I don't like relying on Excel formulae too much, unless for clearly-defined problems (like yours, as I understood it initially). Excel formulae deliver still the best solution for what you really want (although its complexity is right "in the limit"). To account for the situation as described above, you can rely on MATCH. If your cells contain text (at least one letter per cell), the code can be changed into:
notUsed.Value2 = "=MATCH(REPT(\"z\",255)," + targetCol + ":" + targetCol + ")";
In case of having numeric values (not a single letter in the cell):
notUsed.Value2 = "=MATCH(LOOKUP(" + Int32.MaxValue.ToString() + "," + targetCol + ":" + targetCol + ")," + targetCol + ":" + targetCol + ")";
If you want to account for both options, you would have to combine these equations: you can create a new formula including both; or you might rely on C# code (e.g., get the values from both equations and consider only the bigger one).
Bear also in mind that you have to account for cases where no matches are found. Here you have a code accounting for both situations (letters and numbers via C# code) and for no matches:
notUsed.Value2 = "=MATCH(REPT(\"z\",255)," + targetCol + ":" + targetCol + ")";
int lastLetter = Convert.ToInt32(notUsed.Value2);
if (lastLetter == -2146826246)
{
lastLetter = 0;
}
totRows = lastLetter;
notUsed.Value2 = "=MATCH(LOOKUP(" + Int32.MaxValue.ToString() + "," + targetCol + ":" + targetCol + ")," + targetCol + ":" + targetCol + ")";
int lastNumber = Convert.ToInt32(notUsed.Value2);
if (lastNumber == -2146826246)
{
lastNumber = 0;
}
if (lastNumber > totRows)
{
totRows = lastNumber;
}

This should do it:
private static int GetRowsInColumnOnWorkSheetInWorkbook(string workbookName, int worksheetNumber, int workSheetColumn)
{
return new Excel.Application().Workbooks.Open(workbookName)
.Sheets[worksheetNumber]
.UsedRange
.Columns[workSheetColumn]
.Rows
.Count;
}
You could have the following override also:
private static int GetRowsInColumnOnWorkSheetInWorkbook(string workbookName, string worksheetName, int workSheetColumn)
{
return new Excel.Application().Workbooks.Open(workbookName)
.Sheets[worksheetName]
.UsedRange
.Columns[workSheetColumn]
.Rows
.Count;
}
It's slightly longer than the other answer, but I think this is more readable, and simpler.

Find string in text, remove the first and last char

I search in a text for some strings and want to remove the first and last char in those strings.
Example :
...
...
OK 125 ab_D9 "can be "this" or; can not be "this" ";
...
OK 673 e_IO1_ "hello; is strong
or maybe not strong";
...
So I use the code to find all strings begin with OK and remove from the 4 groups "...":
tmp = fin.ReadToEnd();
var matches = Regex.Matches(tmp, "(OK) ([0-9]+) ([A-Za-z_0-9]+) (\"(?:(?!\";).)*\");", RegexOptions.Singleline);
for (int i = 0; i < matches.Count; i++)
{
matches[i].Groups[4].Value.Remove(0);
matches[i].Groups[4].Value.Remove(matches[i].Groups[4].Value.ToString().Length - 1);
Console.WriteLine(matches[i].Groups[1].Value + "\r\n" + "\r\n" + "\r\n" + matches[i].Groups[2].Value + "\r\n" + "\r\n" + matches[i].Groups[3].Value + "\r\n" + "\r\n" + "\r\n" + matches[i].Groups[4].Value);
Console.WriteLine(" ");
}
But it doesn't remove first and last char from Group 4. What did I do wrong?
My Result should be:
OK
125
ab_D9
can be "this" or; can not be "this"
OK
673
e_IO1
hello; is strong
or maybe not strong

There is no need to remove things. Just don't capture the quotes in the first place. So move the parentheses one character inward.
"(OK) ([0-9]+) ([A-Za-z_0-9]+) \"((?:(?!\";).)*)\";"

You should assign the result of Substring() and Remove() methods. they do not change the existing string but return the changed string which you need to assign to the same or some other string variable. Check the code:
tmp = fin.ReadToEnd();
var matches = Regex.Matches(tmp, "(OK) ([0-9]+) ([A-Za-z_0-9]+) (\"(?:(?!\";).)*\");", RegexOptions.Singleline);
for (int i = 0; i < matches.Count; i++)
{
string str = matches[i].Groups[4].Value.Substring(0);
str = str.Remove(str.Length - 1);
Console.WriteLine(matches[i].Groups[1].Value + "\r\n" + "\r\n" + "\r\n" + matches[i].Groups[2].Value + "\r\n" + "\r\n" + matches[i].Groups[3].Value + "\r\n" + "\r\n" + "\r\n" + str);
Console.WriteLine(" ");
}
P.S. You should use Environment.NewLine instead of "\r\n", it's the better approach.