Develop Reference

C#, Windows application, draw a square with side N

for school practice I have to make a windows application in C# that takes a input number and draws a square of X's with side N. I have to do it with a loops and i can't use any preset commands. (For example math.pow i cannot use) (I've included a picture of the assignment.) I've already mode this program in a console application and there it worked fine.
I think that i'm very close of solving it but can't figure out what the last step is. I would love to know what i'm missing and how i should solve this.
See the assignment
This is my code now:
int n;
n = int.Parse(txt_input.Text);
//upper part
for (int i = 0; i < n; i++)
{
lbl_output.Text = "X";
lbl_output.Text = "\n";
}
//middel part
for (int i = 0; i < n - 2; i++)
{
lbl_output.Text = "X";
for (int j = 0; j < n - 2; j++) lbl_output.Text = " ";
lbl_output.Text = "X";
lbl_output.Text = "\n";
}
//upper part
for (int i = 0; i < n; i++)
{
lbl_output.Text = "X";
lbl_output.Text = "\n";
}

Try this:
int n = int.Parse(txt_input.Text);
var sb = new StringBuilder();
for (int j = 0; j < n; j++)
{
sb.Append('X');
}
sb.AppendLine();
for (int i = 0; i < n - 2; i++)
{
sb.Append('X');
for (int j = 0; j < n - 2; j++)
{
sb.Append(' ');
}
sb.Append('X');
sb.AppendLine();
}
for (int j = 0; j < n; j++)
{
sb.Append('X');
}
lbl_output.Text = sb.ToString();

Try this;
int n = int.Parse(txt_input.Text);
//upper part
for (int i = 0; i < n; i++)
{
lbl_output.Text += "X";
}
lbl_output.Text += "\n";
//middel part
for (int i = 0; i < n - 2; i++)
{
lbl_output.Text += "X";
for (int j = 0; j < n - 2; j++)
lbl_output.Text += " ";
lbl_output.Text += "X";
lbl_output.Text += "\n";
}
//upper part
for (int i = 0; i < n; i++)
{
lbl_output.Text += "X";
}
You forget to use += which will append the text with the previous assigned text. Also you had some unnecessary new lines in your code.

Need to append to the string. There's a couple ways of doing this. Tho '+=' should work fine. += is short for variable = variable + newValue
int n = int.Parse(txt_input.Text);
string output = "";
for(int x = 0; x < n; x++) //rows
{
if (x == 0 || x == n-1) //first / last row all x
for(int y = 0; y < n; y++)
{
output += "x";
}
else //other rows
for(int y = 0; y < n; y++)
{
output += (y == 0 || y == n - 1) ? "x" : " "; //if first or last column "X" else " "
}
output += "\n"; //at the end of each row a return
}
lbl_output.Text = output;
You can see it run in the browser here: https://dotnetfiddle.net/wiYfjX

Use two loops. One for the width of the square and one for the height of the square.
Give this a try and replace the parameter from what is in the txt_input control. (Just place the function whereever you want in your code (button_click for example) instead of the form load.
private void Form1_Load(object sender, EventArgs e)
{
lblOutput.Text = GenerateSquare(5);
}
private string GenerateSquare(int n)
{
string square = "";
for (int w = 0; w < n; w++)
{
for (int h = 0; h < n; h++)
{
// top or bottom line
if (w == 0 || w == n - 1)
{
square += "x";
}
else // sides
{
if (h == 0 || h == n - 1)
{
square += "x";
}
else square += " ";
}
// change line
if (h == n - 1)
square += "\n";
}
}
return square;
}

How to process an array correctly

Here's the part 1 of my question, if you wanna check the background of this question :
Detecting brackets in input string
Forgive me if the title doesn't match, since I also confused how to name it appropriately to picture my problem. If anyone knows a more appropriate title, feel free to edit.
So, given below code (my own code) :
private const int PARTICLE_EACH_CHAR = 4;
/*ProcessBarLines : string s only contains numbers, b, [, and ]*/
private int ProcessBarLines(Canvas canvas, string s, int lastLineAboveNotation)
{
List<int> bracket = new List<int>();
List<int> other = new List<int>();
int currentCloseNumber = 0;
int currentOpenNumber = 0;
for (int i = 0; i < s.Length; i++)
{
if (s[i] == '[')
{
bracket.Add(i);
currentOpenNumber++;
if (i - 1 > 0 && s[i - 1] != '[')
{
currentOpenNumber = 1;
}
}
else if (s[i] == ']')
{
bracket.Add(i);
currentCloseNumber++;
if (i + 1 >= s.Length || s[i + 1] != ']' || currentOpenNumber == currentCloseNumber)
{
int min = bracket.Count - (currentCloseNumber * 2);
int max = bracket[bracket.Count - 1];
List<int> proc = new List<int>();
int firstIndex = -1;
int lastIndex = -1;
for (int ii = 0; ii < other.Count; ii++)
{
if (other[ii] > min && other[ii] < max)
{
proc.Add(other[ii]);
if (firstIndex == -1)
{
firstIndex = ii;
lastIndex = ii;
}
else
{
lastIndex = ii;
}
}
}
double leftPixel = firstIndex * widthEachChar;
double rightPixel = (lastIndex * widthEachChar) + widthEachChar;
DrawLine(canvas, currentCloseNumber, leftPixel,
rightPixel, lastLineAboveNotation * heightEachChar / PARTICLE_EACH_CHAR);
lastLineAboveNotation += currentCloseNumber - 1;
currentOpenNumber -= currentCloseNumber;
currentCloseNumber = 0;
}
}
else
{
other.Add(i);
}
}
return lastLineAboveNotation + 1;
}
Here's the test cases :
Picture 1 & 2 is the correct answer, and picture 3 is the wrong answer. Picture 3 should have a line, just like inverted from number 2, but, apparently, (if you look closely) the line is drawn on the right, but it should be on the left to be correct (above 0).
I figured, the problem is, I'm quite sure on the "min". Since it doesn't give the correct starting value.
Any idea on this? Feel free to clarify anything. It's used for writing numeric musical scores.
Btw, DrawLine() just meant to draw the line above the numbers, it's not the problem.

Finally! I found it!
private int ProcessBarLines(Canvas canvas, string s, int lastLineAboveNotation)
{
List<int> bracket = new List<int>();
List<int> other = new List<int>();
int currentCloseNumber = 0;
int currentOpenNumber = 0;
int space = 0;
for (int i = 0; i < s.Length; i++)
{
if (s[i] == '[')
{
bracket.Add(i);
currentOpenNumber++;
if (i - 1 > 0 && s[i - 1] != '[')
{
currentOpenNumber = 1;
}
}
else if (s[i] == ']')
{
bracket.Add(i);
currentCloseNumber++;
if (i + 1 >= s.Length || s[i + 1] != ']' || currentOpenNumber == currentCloseNumber)
{
int min = bracket[Math.Max(bracket.Count - ((currentCloseNumber * 2) + space), 0)];
int max = bracket[bracket.Count - 1];
space = max - min - 1;
List<int> proc = new List<int>();
int firstIndex = -1;
int lastIndex = -1;
for (int ii = 0; ii < other.Count; ii++)
{
if (other[ii] > min && other[ii] < max)
{
proc.Add(other[ii]);
other[ii] = -1;
if (firstIndex == -1)
{
firstIndex = ii;
lastIndex = ii;
}
else
{
lastIndex = ii;
}
}
}
double leftPixel = firstIndex * widthEachChar;
double rightPixel = (lastIndex * widthEachChar) + widthEachChar;
DrawLine(canvas, currentCloseNumber, leftPixel,
rightPixel, lastLineAboveNotation * heightEachChar / PARTICLE_EACH_CHAR);
lastLineAboveNotation += 1;
currentOpenNumber -= currentCloseNumber;
currentCloseNumber = 0;
}
}
else
{
other.Add(i);
}
}
return lastLineAboveNotation + 1;
}
If someone got a more efficient code, please let us know!

How to get minimum value from 2D array in c# and the indices of that cell?

I want to get the minimum value from 2 dimensional array [1024,9] ,and I want the position of this minimum value.
Hint: the last column is flag "if flag == 0 : check this row, else : skip this row"
I tried this cod ,but it did not help me ...
float min = fill_file[0, 0];
int ind = 0;
int ind2 = 0;
for (int i = 0; i < 1024; i++)
{
for (int j = 0; j < 8; j++)
{
if (fill_file[i, j] < min && fill_file[i, 8] == 0)
{
min = fill_file[i, j];
ind2 = i;
ind = j;
}
}
}
This is all code based on your request
int t = 0;
while (t < 1024)
{
float min = fill_file[0, 0];
int ind = 0;
int ind2 = 0;
for (int i = 0; i < 1024; i++)
{
for (int j = 0; j < 8; j++)
{
if (fill_file[i, j] < min && fill_file[i, 8] == 0)
{
min = fill_file[i, j];
ind2 = i;
ind = j;
}
}
}
machens[ind] = machens[ind] + min;
fill_file[ind2, 8] = 1;
for (int r = 0; r < 1024; r++)
{
if (fill_file[r, 8] != 1)
fill_file[r, ind] = fill_file[r, ind] + min;
}
t++;
}//End while

Firstly:
If it happens that none of the rows have the "use this row" flag set to zero (with zero meaning "use this row"), you will obviously get a wrong result.
I guess this will never happen for your data?
Secondly:
If fill_file[0,8] is nonzero, you will still be initialising min to fill_file[0,0] even though the flag says you shouldn't use that row.
In that case, if fill_file[0,0]happens to be less than all the values in any of the rows for which fill_file[row,8] is zero then you will get the wrong result.
I would be tempted to initialise min to float.MaxValue and ind and ind2 to -1 each, so you know if they haven't been updated.
And call them minRow and minCol.
Thirdly:
There's an obvious optimisation: If [row,8] is nonzero, there's no point in running the inner iteration for that row.
Putting this all together:
float minValue = float.MaxValue;
int minCol = -1;
int minRow = -1;
for (int row = 0; row < 1024; row++)
{
if (fill_file[row, 8] == 0)
{
for (int col = 0; col < 8; col++)
{
if (fill_file[row, col] < minValue)
{
minValue = fill_file[row, col];
minRow = row;
minCol = col;
}
}
}
}
// If minRow is < 0, then no valid data exists.
// Otherwise, fill_file[minRow, minCol] contains minVal

This code:
var min_ij = Enumerable.Range(0, 1024)
.Where(i => fillFile[i, 9] == 0)
.SelectMany(i => Enumerable.Range(0, 8)
.Select(j => new { i, j }))
.ArgMin(ij => fillFile[ij.i, ij.j]);
int min_i = min_ij.i;
int min_j = min_ij.j;
Using this helper function:
public static TElem ArgMin<TElem, TField>(this IEnumerable<TElem> set, Func<TElem, TField> objective, bool allowEmptySet = false)
where TField : IComparable<TField>
{
if (!set.Any() && !allowEmptySet)
throw new InvalidOperationException("Cannot perform ArgMin on an empty set.");
bool first = true;
TElem bestElem = default(TElem);
TField bestObjective = default(TField);
foreach (TElem currElem in set)
{
TField currObjective = objective(currElem);
if (first || currObjective.CompareTo(bestObjective) < 0)
{
first = false;
bestElem = currElem;
bestObjective = currObjective;
}
}
return bestElem;
}

This is a straightforward problem. Try something like this:
static void Main( string[] args )
{
int[,] values = new int[1024,9];
Random rng = new Random() ;
// initialise the array
for ( int r = 0 ; r < 1024 ; ++r )
{
for ( int c = 0 ; c < 9 ; ++c )
{
values[r,c] = rng.Next() ;
}
int x = rng.Next(10) ;
if ( x == 1 )
{
values[r,8] = 0 ;
}
}
int? minValue = null ;
int? minRow = null ;
int? minCol = null ;
for ( int r = 0 ; r < 1024 ; ++r )
{
bool skipRow = 0 == values[r,8] ;
if ( skipRow ) continue ;
for ( int c = 0 ; c < 8 ; ++c )
{
int cell = values[r,c] ;
if ( !minValue.HasValue || cell < minValue )
{
minValue = cell ;
minRow = r ;
minCol = c ;
}
}
}
// display the results
if ( minValue.HasValue )
{
Console.WriteLine( "Minimum: values[{0},{1}] is {2}" , minRow , minCol , minValue );
}
else
{
Console.WriteLine( "all rows skipped" );
}
return ;
}

Declaring of arrays in C#

I have written the following code in an effort to try and compute the values down there below, but all my arrays do not work; especially the ones in the for loops. Can someone help teach me how to declare an array inside a loop? They keep showing errors like "Did you miss declaring a new object?"
Thanks
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
class Program
{
public class seasonal
{
public float mTotal;
public float movingAverage;
public int y;
public char quarter;
public char ssq;
public int rank;
public float forecast;
public float centralMovingAverage;
public float cmTotal;
public float sSeasonal;
}
public static int i;
public static int j;
public static int k = 0;
public static int n;
static void Main(string[] args)
{
int x; int r; int m; int c; int u = 0;
seasonal temp = new seasonal();
int n1; int n2; int n3; int n4; int sumr1 = 0; int sumr2 = 0; int sumr3 = 0; int sumr4 = 0;
float h; float ss; float sum; float sums1 = 0; float sums2 = 0; float sums3 = 0; float sums4 = 0; float tsums;
Console.WriteLine("Enter the no. of observations");
string nObservations = Console.ReadLine();
n = Convert.ToInt32(nObservations);
seasonal[] seasonal = new seasonal[n];
seasonal[] s = new seasonal[n];
for (i = 0; i < n; i++)
{
Console.Write("{0:D}:", (i+1) );
string value = Console.ReadLine();
int observation = Convert.ToInt32(value);
seasonal thisSeasonal = new seasonal();
thisSeasonal.y = observation;
seasonal[i] = thisSeasonal;
if (i>=0 && i<3)
{
seasonal[i].quarter = '1';
}
if (i>=3 && i<6)
{
seasonal[i].quarter = '2';
}
if (i>=6 && i<9)
{
seasonal[i].quarter = '3';
}
if (i>=9 && i<12)
{
seasonal[i].quarter = '4';
}
if (i>12)
{
r = i % 12;
if (r>=0 && r<3)
{
seasonal[i].quarter = '1';
}
if (r>=3 && r<6)
{
seasonal[i].quarter = '2';
}
if (r>=6 && r<9)
{
seasonal[i].quarter = '3';
}
if (r>=9 && r<12)
{
seasonal[i].quarter = '4';
}
}
for (i = k; i < n-3; i++)
{
sum = 0;
for (j = u+k; j < 4+k; j++)
{
sum += seasonal[j].y;
seasonal[i].mTotal = sum;
seasonal[i].movingAverage = seasonal[i].mTotal / 4;
Console.Write("{0:f}", seasonal[i].movingAverage);
k++;
}
}
for ( i = 0; i < (n-4); i++)
{
ss = 0;
for (j = 0; j < (2+i); j++)
{
ss += seasonal[j].movingAverage;
}
seasonal[i].cmTotal = ss;
seasonal[i].centralMovingAverage = seasonal[i].cmTotal / 2;
seasonal[i].sSeasonal = (seasonal[i+2].y)/(seasonal[i].centralMovingAverage);
if (i == 0 || i % 4 == 0)
{
seasonal[i].ssq = '3';
}
if (i == 1 || i % 4 == 1)
{
seasonal[i].ssq = '4';
}
if (i == 2 || i % 4 == 2)
{
seasonal[i].ssq = '1';
}
if (i == 3 || i % 4 == 3)
{
seasonal[i].ssq = '2';
}
Console.Write("\n{0:f}", seasonal[i].centralMovingAverage);
Console.Write("\n {0:f}", seasonal[i].sSeasonal);
}
}
for (m= 0; m < n; m++)
{
s[m] = seasonal[m];
}
for ( i = 0; i < (n-5); i++)
{
for ( j = 0; j < (n-4); j++)
{
if (s[i].sSeasonal > s[j].sSeasonal)
{
temp = s[i];
s[i] = s[j];
s[j] = temp;
}
}
}
for ( k = 0; k < (n-4); k++)
{
s[k].rank = k + 1;
Console.Write("\n\t {0:D}", s[k].rank);
}
for ( i = 0; i < (n-4); i++)
{
if (s[i].ssq == '1')
{
sumr1 += s[i].rank;
sums1 += s[i].sSeasonal;
//n1 ++;
}
if (s[i].ssq == '2')
{
sumr2 += s[i].rank;
sums2 += s[i].sSeasonal;
//n2++;
}
if (s[i].ssq == '3')
{
sumr3 += s[i].rank;
sums3 += s[i].sSeasonal;
//n3++;
}
if (s[i].ssq == '4')
{
sumr4 += s[i].rank;
sums4 += s[i].sSeasonal;
//n4++;
}
}
tsums = ((sums1/4)+(sums2/4)+(sums3/4)+(sums4/4));
Console.Write("\n\n\n{0:f}",tsums);
Console.Write("\n\n\n\n\n{0:D}",sumr1);
Console.Write("\n\n\n\n{0:D}",sumr2);
Console.Write("\n\n\n\n{0:D}",sumr3);
Console.Write("\n\n\n\n\n{0:D}",sumr4);
Console.Write("\n{0:f}",sums1/4);
Console.Write("\n\n{0:f}",sums2/4);
Console.Write("\n\n{0:f}",sums3/4);
Console.Write("\n\n{0:f}",sums4/4);
Console.Write("\n{0:f}",((sums1/4)/tsums)*4);
Console.Write("\n\n{0:f}",((sums2/4)/tsums)*4);
Console.Write("\n\n{0:f}",((sums3/4)/tsums)*4);
Console.Write("\n\n{0:f}",((sums4/4)/tsums)*4);
}
}
}

You need to initialise the objects in your arrays:
Seasonal[] seasonal = new Seasonal[n];
for (int l = 0; l < seasonal.Length; l++)
{
seasonal[l] = new Seasonal();
}
Seasonal[] s = new Seasonal[n];
for (int l = 0; l < s.Length; l++)
{
s[l] = new Seasonal();
}
This only solves the initialisation problem, though. You may want to look at naming conventions for readability, and then the index off by 1 you'll experience at roughly line 105.

instead of working with
seasonal[] seasonal = new seasonal[n];
seasonal[] s = new seasonal[n];
do work with
seasonal[] s1 = new seasonal[n];
seasonal[] s2 = new seasonal[n];
But when I see code like, this, where you just copy your array:
for (m= 0; m < n; m++)
{
s[m] = seasonal[m];
}
why would you do that? copy the entire array instead of every single entry..
why do you not use any c# constructs?

The problem is this line:
sum += seasonal[j].y;
But there isn't a simple fix. You are creating each object individually through the loop instead of before you enter the loop so each iteration is looking at null objects. Also, the loop this line is in reads past the end of the array. The code is a bit complex to easily see what you're trying to do and how to fix it.

Just an example for to simplify some of your code:
you wrote the following:
if (i>=0 && i<3)
{
seasonal[i].quarter = '1';
}
if (i>=3 && i<6)
{
seasonal[i].quarter = '2';
}
if (i>=6 && i<9)
{
seasonal[i].quarter = '3';
}
if (i>=9 && i<12)
{
seasonal[i].quarter = '4';
}
if (i>12)
{
r = i % 12;
if (r>=0 && r<3)
{
seasonal[i].quarter = '1';
}
if (r>=3 && r<6)
{
seasonal[i].quarter = '2';
}
if (r>=6 && r<9)
{
seasonal[i].quarter = '3';
}
if (r>=9 && r<12)
{
seasonal[i].quarter = '4';
}
}
you could write that instead:
if(i >= 0)
seasonal[i].quarter = (((i % 12)/3) + 1).ToString();

I don' think this code
seasonal[] seasonal = new seasonal[n];
seasonal[] s = new seasonal[n];
is correct. Try
seasonal[] seas = (seasonal[])Array.CreateInstance(typeof(seasonal), n);

How can I optimize my implementation of the "toExponential" algorithm to improve precision?

I feel like my implementation is a bit naive. Take notice of the variables min in max which have a rather small precision of +/- 0.0001. If I raise the precision any further the code is just too slow.
Algorithm
alt text http://img35.imageshack.us/img35/2060/toexponential.jpg
Code
private IDynamic ToExponential(Engine engine, Args args)
{
var x = engine.Context.ThisBinding.ToNumberPrimitive().Value;
if (double.IsNaN(x))
{
return new StringPrimitive("NaN");
}
var s = "";
if (x < 0)
{
s = "-";
x = -x;
}
if (double.IsPositiveInfinity(x))
{
return new StringPrimitive(s + "Infinity");
}
var f = args[0].ToNumberPrimitive().Value;
if (f < 0D || f > 20D)
{
throw new Exception("RangeError");
}
var m = "";
var c = "";
var d = "";
var e = 0D;
var n = 0D;
if (x == 0D)
{
f = 0D;
m = m.PadLeft((int)(f + 1D), '0');
e = 0;
}
else
{
if (!args[0].IsUndefined) // fractionDigits is supplied
{
var lower = (int)Math.Pow(10, f);
var upper = (int)Math.Pow(10, f + 1D);
var min = 0 - 0.0001;
var max = 0 + 0.0001;
for (int i = lower; i < upper; i++)
{
for (int j = (int)f; ; --j)
{
var result = i * Math.Pow(10, j - f) - x;
if (result > min && result < max)
{
n = i;
e = j;
goto Complete;
}
if (result <= 0)
{
break;
}
}
for (int j = (int)f + 1; ; j++)
{
var result = i * Math.Pow(10, j - f) - x;
if (result > min && result < max)
{
n = i;
e = j;
goto Complete;
}
if (result >= 0)
{
break;
}
}
}
}
else
{
var min = x - 0.0001;
var max = x + 0.0001;
// Scan for f where f >= 0
for (int i = 0; ; i++)
{
// 10 ^ f <= n < 10 ^ (f + 1)
var lower = (int)Math.Pow(10, i);
var upper = (int)Math.Pow(10, i + 1D);
for (int j = lower; j < upper; j++)
{
// n is not divisible by 10
if (j % 10 == 0)
{
continue;
}
// n must have f + 1 digits
var digits = 0;
var state = j;
while (state > 0)
{
state /= 10;
digits++;
}
if (digits != i + 1)
{
continue;
}
// Scan for e in both directions
for (int k = (int)i; ; --k)
{
var result = j * Math.Pow(10, k - i);
if (result > min && result < max)
{
f = i;
n = j;
e = k;
goto Complete;
}
if (result <= i)
{
break;
}
}
for (int k = (int)i + 1; ; k++)
{
var result = i * Math.Pow(10, k - i);
if (result > min && result < max)
{
f = i;
n = j;
e = k;
goto Complete;
}
if (result >= i)
{
break;
}
}
}
}
}
Complete:
m = n.ToString("G");
}
if (f != 0D)
{
m = m[0] + "." + m.Substring(1);
}
if (e == 0D)
{
c = "+";
d = "0";
}
else
{
if (e > 0D)
{
c = "+";
}
else
{
c = "-";
e = -e;
}
d = e.ToString("G");
}
m = m + "e" + c + d;
return new StringPrimitive(s + m);
}
Final Version
I swear someone must have hit me with a particularly large hammer back when I originally wrote this...
private IDynamic ToExponential(Engine engine, Args args)
{
var x = engine.Context.ThisBinding.ToNumberPrimitive().Value;
if (args[0].IsUndefined)
{
return new StringPrimitive(x.ToString("0.####################e+0"));
}
var f = args[0].ToNumberPrimitive().Value;
if (f < 0D || f > 20D)
{
RuntimeError.RangeError("The parameter fractionDigits must be between 0 and 20.");
}
return new StringPrimitive(x.ToString("0." + string.Empty.PadRight((int)f, '0') + "e+0"));
}

When you compute result = i * Math.Pow(10, j - f) - x you're trying to find where result is 0. Since j, f, and x are know, you just need to solve for i. Rather than writing a loop to find i, you can just say
i * Math.Pow(10, j - f) = x => i = x / Math.Pow(10, j - f)
The value you need should be either floor(i) or ceil(i).
Just out of curiosity, have you checked to see if ToString("e") gives you the correct answer?

I'd start by using Math.Log10, rather than a loop, to find the exponent.