Many else and if statements? - c#

I am reading a csv file which has column names in first line and values in line >1. I need to get the position of the column name. The only way I can think of is to do either switch or ifs. I read it somewhere that in my case , it is faster (better) to do the ifs. However the file has many columns (~120). Just wondering if there is an alternative(s).
private static void Get_Position(string line, performance p)
{
string[] line_split = line.Split(',');
for (int i = 0; i < line_split.Length; i++)
{
if (line_split[i].Contains(#"(0)\% Processor Time"))
{
p.percore[0] = i;
}
else if (line_split[i].Contains(#"(1)\% Processor Time"))
{
p.percore[1] = i;
}
else if (line_split[i].Contains("Private Bytes"))
{}
else if (line_split[i].contains("DPC")
{
}
//on and on and on with else ifs

What is preventing you from using a loop?
for (int i = 0; i < line_split.Length; i++)
{
for(var j = 0; j < 120; j++)
{
if(line_split[i].Contains(#"(" + j + ")\% Processor Time"))
{
p.percore[j] = i;
}
}
...
To maintain the same functionality as if else if then you could use a break inside the conditional.
Edit: The edit now made it clear that there is no clear pattern to the string in contains. Still, if you are writing out 120 if/else if statements you should store what you will be looking for in some type of collection. For example, a List would work. Then access the index j of the collection in your loop:
...
var listOfSearchItems = new List<string>() { "Private Bytes", "DPC" };
for (int i = 0; i < line_split.Length; i++)
{
for(var j = 0; j < 120; j++)
{
if(line_split[i].Contains(listOfSearchItems[j])
{
p.percore[j] = i;
}
}
...

Related

Comparing two variable in a structure C#

What I want to do is compare two of the same variable in a structure.
For example I have a structure like so:
struct player
{
public string name;
public int number;
}
static player[] players = new player[3];
and what I want to do is compare the numbers, so that if two players have the same number, something will happen.
This is what I tried, however it would always say two numbers were the same because it would compare two of the same
for (int i = 0; i < length; i++)
{
for (int j = 0; j < length; j++)
{
if (players[i].number == players[j].number)
{
Console.WriteLine("Same");
Console.ReadLine();
}
else
{
Console.WriteLine("Not");
Console.ReadLine();
}
}
Hopefully you understand what I mean.
Any help would be really appreciated!
Thanks
Problem is in your loop variables i and j starting both at index zero. Then you are comparing element zero to element zero and therefore the condition is true.
Update this line:
for (int j = 0; j < length; j++)
to this:
for (int j = i + 1; j < length; j++)
Edit
To be more precise. The condition evaluates to true not only for the first element, but for each element when i and j are the same. This solution bars both control variables from having the same value in any iteration.
Simple, just add a check to make sure you aren't comparing the same index, because this is the same object:
for (int i = 0; i < length; i++)
{
for (int j = 0; j < length; j++)
{
if (i == j) continue;
if (players[i].number == players[j].number)
{
Console.WriteLine("Same");
Console.ReadLine();
}
else
{
Console.WriteLine("Not");
Console.ReadLine();
}
}
Use a Class, and do it using Linq:
public class Player
{
public string Name { get; set; }
public int Number { get; set; }
}
Then in the other class have this method to cross-check
private void Match()
{
var players = new Player[3].ToList();
foreach (var found in players.ToList().Select(player => players.FirstOrDefault(p => p.Number == player.Number)))
{
if (found != null)
{
Console.WriteLine("Same");
Console.ReadLine();
}
else
{
Console.WriteLine("Not");
Console.ReadLine();
}
}
}

What is the most efficient way to find the largest element in a matrix along with position? Also, the largest element in each column with position

I have written the following code but it looks to be far from efficient.
//Find largest in tempRankingData
int largestIntempRankingData = tempRankingData[0, 0];
for (int i = 0; i < count; i++)
{
for (int j = 0; j < count; j++)
{
if (tempRankingData[i, j] > largestIntempRankingData)
{
largestIntempRankingData = tempRankingData[i, j];
}
}
}
//Find position of largest in tempRankingData
List<string> positionLargestIntempRankingData = new List<string>();
for (int i = 0; i < count; i++)
{
for (int j = 0; j < count; j++)
{
if (tempRankingData[i, j] == largestIntempRankingData)
{
positionLargestIntempRankingData.Add(i + "," + j);
}
}
}
//Find largest in each column
int largestInColumn = 0;
List<string> positionOfLargestInColumn = new List<string>();
Dictionary<int, List<string>> position = new Dictionary<int, List<string>>();
for (int i = 0; i < count; i++)
{
largestInColumn = tempRankingData[0, i];
positionOfLargestInColumn = new List<string>();
for (int j = 0; j < count; j++)
{
if (tempRankingData[j, i] > largestInColumn)
{
largestInColumn = tempRankingData[j, i];
}
}
for (int j = 0; j < count; j++)
{
if (tempRankingData[j, i] == largestInColumn)
{
positionOfLargestInColumn.Add(j + "," + i);
}
}
position.Add(i, positionOfLargestInColumn);
}
So, I wanted to check about the most efficient way to do this.
Whilst you're finding the largest in each column, you could also be finding the largest overall. You can also capture the positions as you go:
//Find largest in each column
int largestInColumn = 0;
int largestOverall = int.MinValue;
List<string> positionOfLargestInColumn;
Dictionary<int, List<string>> position = new Dictionary<int, List<string>>();
List<string> positionLargestIntempRankingData = new List<string>();
for (int i = 0; i < count; i++)
{
largestInColumn = tempRankingData[0, i];
positionOfLargestInColumn = new List<string>();
positionOfLargestInColumn.Add("0," + i);
for (int j = 1; j < count; j++)
{
if (tempRankingData[j, i] > largestInColumn)
{
largestInColumn = tempRankingData[j, i];
positionOfLargestInColumn.Clear();
positionOfLargestInColumn.Add(j + "," + i);
}
else if(tempTankingData[j,i] == largestInColumn)
{
positionOfLargestInColumn.Add(j + "," + i);
}
}
position.Add(i, positionOfLargestInColumn);
if(largestInColumn > largestOverall)
{
positionLargestIntempRankingData.Clear();
positionLargestIntempRankingData.AddRange(positionOfLargestInColumn);
largestOverall = largestInColumn;
}
else if(largestInColumn == largestOverall)
{
positionLargestIntempRankingData.AddRange(positionOfLargestInColumn);
}
}
1). You can find largest element and its position in one method and retrieve.
Would be caller of your method concerned about position or actual value, is a matter of concrete case.
2) You can use `yield return' technique in your matrix search (for column based search), so do not compute all column's maximas and push them into the dictionary. Dictionaries are not that fast as arrays, if you can avoid use them, do that.
3) You can keep a matrix in single dimension, long array. Have [] access operator overload, to "emulate" matrix access. Why ? If finding maximum is something frequent you might need to do during program run, having one foreach loop is faster then having 2 nested once. In case of a big matrices, single array search can be easily parallelized among different cores.
If big matrices and/or frequent calls are not your concern, just simplify your code like in points (1), (2).
For your fist two itterations you could replace with this:
//Find largest in tempRankingData
int largestIntempRankingData = tempRankingData[0, 0];
List<KeyValuePair<double,string>> list = new List<KeyValuePair<double,string>>();
for (int i = 0; i < count; i++)
{
for (int j = 0; j < count; j++)
{
if (tempRankingData[i, j] > largestIntempRankingData)
{
largestIntempRankingData = tempRankingData[i, j];
list.Add(new KeyValuePair<double, string>(largestIntempRankingData, i + "," + j)); //Add the value and the position;
}
}
}
//This gives a list of strings in which hold the position of largestInItemRankingData example "3,3"
//Only positions where the key is equal to the largestIntempRankingData;
list.Where(w => w.Key == largestIntempRankingData).ToList().Select(s => s.Value).ToList();
You can get all these pieces of information in a single scan with a little fiddling around. Something like this (converting the rows and columns to a string is trivial and better done at the end anyway):
int? largestSoFar = null; // you could populate this with myMatrix[0,0]
// but it would fail if the matrix is empty
int largestCol = 0;
int largestRow = 0;
int?[] largestPerColumn = new int?[numOfCols]; // You could also populate this with
// the values from the first row but
// it would fail if there are no rows
int[] largestColumnRow = new int[numOfCols];
for (int i = 0; i < numOfRows; i++)
{
for (int j = 0; j < numOfCols; i++)
{
if (largestSoFar < myMatrix[i,j])
{
largestSoFar = myMatrix[i,j];
largestCol = j;
largestRow = i;
}
if (largestPerColumn[j] < myMatrix[i,j])
{
largestPerColumn[j] = myMatix[i,j];
largestColumnRow[j] = i;
}
}
}
// largestSoFar is the biggest value in the whole matrix
// largestCol and largestRow is the column and row of the largest value in the matrix
// largestPerColumn[j] is the largest value in the jth column
// largestColumnRow[j] is the row of the largest value of the jth column
If you do need to capture all the "maxima" (for want of a better word, because that's not really what you are doing) in a column, you could just change the above code to something like this:
int? largestSoFar = null; // you could populate this with myMatrix[0,0]
// but it would fail if the matrix is empty
int largestCol = 0;
int largestRow = 0;
int?[] largestPerColumn = new int?[numOfCols]; // You could also populate this with
// the values from the first row but
// it would fail if there are no rows
List<int>[] largestColumnRow = new List<int>[numOfCols];
for (int i = 0; i < numOfRows; i++)
{
for (int j = 0; j < numOfCols; i++)
{
if (largestSoFar < myMatrix[i,j])
{
largestSoFar = myMatrix[i,j];
largestCol = j;
largestRow = i;
}
if (largestPerColumn[j] < myMatrix[i,j])
{
largestPerColumn[j] = myMatix[i,j];
largestColumnRow[j].Add(i);
}
}
}
// Now largestColumnRow[j] gives you a list of all the places where you found a larger
// value for the jth column

Function not returning array

I have this function to initiate a two dimensional array:
static Array Matrix(int Rows, int Columns)
{
int[,] LotteryArray = new int[Rows,Columns];
for (int i = 0; i < LotteryArray.GetLength(0); i++)
{
for (int j = 0; j < LotteryArray.GetLength(1); j++)
{
LotteryArray[i, j] = RandomNum(1, 46);
Console.Write("{0,3},", LotteryArray[i, j]);
}
Console.WriteLine();
}
return LotteryArray;
}
Then I have this which is supposed to give me a one dimensional array and see how many numbers in the winning array are in the matrix:
int RowNum = 1;
int Prediction = 0;
Console.WriteLine("Your winning numbers are!");
Console.WriteLine("------------------------");
int[] Winner = new int[6];
for (int i = 0; i < Winner.Length; i++) //this loop is to initiate and print the winning numbers
{
Winner[i] = RandomNum(1, 46); //the numbers are supposed to be between 1 and 45, so i tell it to do it until 46 because the upper limit is exclusive
Console.Write("{0,3},", Winner[i]);
}
Console.WriteLine();
Console.WriteLine("------------------------"); //these two lines are for aesthetics
Matrix(Rows, Columns);
foreach (int i in Winner)
{
for (int j = 0; j<LotteryArray; j++)
{
if (Winner[i] == j)
{
Prediction++;
if (j % 6 == 0) { RowNum++; }
}
Console.WriteLine("you got {0} correct prediction in row number {1}",Prediction,RowNum);
RowNum = 1;
}
}
It's telling me LotteryArray doesn't exist in the current context.
LotteryArray is a variable within another method. You cannot access it in the scope you are showing.
You can do get the return from your method into a variable and then use it.
var LotteryArray = Matrix(Rows, Columns);
foreach (int i in Winner)
{
for (int j = 0; j<LotteryArray; j++)
{
if (Winner[i] == j)
{
Prediction++;
if (j % 6 == 0) { RowNum++; }
}
Console.WriteLine("you got {0} correct prediction in row number {1}",Prediction,RowNum);
RowNum = 1;
}
}
LotteryArray is a variable declared in Matrix method, and is not visible outside.

How to get row number?

I have DataTable and i need to clear all empty columns. So here is code example:
for (var i = 0; i < table.Columns.Count; i++)
{
if (table.Rows.Cast<DataRow>().All(r => string.IsNullOrWhiteSpace(r[i].ToStringOrNull())))
{
table.Columns.RemoveAt(i--);
}
}
Question : How can i get row Number in If-statement ?
Thanks.
If by "row number", you mean the index of a Row object in the Rows collection, then you can't get that directly from the Row object. You can, as suggested in Vlad's comment, use something like this instead:
for (var i = 0; i < table.Columns.Count; i++)
{
if (Enumerable.Range(0, table.Rows.Count).All(
j => string.IsNullOrWhiteSpace(tables.Rows[j][i].ToStringOrNull())))
{
table.Columns.RemoveAt(i--);
}
}
That said, it seems to me that it would be better to process the data such that you visit each row only once. This should at the very least improve data locality, and in some scenarios could significantly improve performance. E.g.:
bool[] keepColumn = new bool[table.Columns.Count];
for (int i = 0; i < table.Rows.Count; i++)
{
for (int j = 0; j < table.Columns.Count; j++)
{
if (!keepColumn[j] &&
!string.IsNullOrWhiteSpace(table.Columns[j].ToStringOrNull()))
{
keepColumn[j] = true;
}
}
}
for (int i = table.Columns.Count - 1; i >= 0; i--)
{
if (!keepColumn[i])
{
table.Columns.RemoveAt(i);
}
}
It's obviously a bit more verbose, but IMHO it would be worth it in this case, because it's processing the data in their natural organization (i.e. tables are naturally rows that have columns, as opposed to columns that have rows).

C# populate array with unique ints No Linq or ArrayLists;

This code is buggy but can't figure out why ... want to populate an array with 7 unique random integers without using arraylists or linq! I know the logic is not okay...
class Program
{
static void Main(string[] args)
{ int current;
int[] numbers = new int[7]; // size of that array
Random rNumber = new Random();
current = rNumber.Next(1, 50);
numbers[0] = current;
Console.WriteLine("current number is {0}", current);
for (int i=1;i<7;i++)
{
current = rNumber.Next(1, 50);
for (int j = 0; j < numbers.Length; j++)
{
do
{
if (current == numbers[j])
{
Console.WriteLine("Duplicate Found");
current = rNumber.Next(1, 50);
}
else
{
numbers[j++] = current;
break;
}
}while (current == numbers[j]);
}//inner for
}//outer for
for (int l = 0; l < 7; l++) // DISPLAY NUMBERS
{
Console.WriteLine(numbers[l]);
}
}// main
}//class
want to populate an array with 7 unique integers without using
arraylists or linq!
int[] list = new int[7];
for (int i = 0; i < list.Length; i++)
{
list[i] = i;
}
EDIT
I changed your inner loop, if the random number is already in the array; create a new random and reset j to 0.
for (int i = 1; i < 7; i++)
{
current = rNumber.Next(1, 50);
for (int j = 0; j < numbers.Length; j++)
{
if (current == numbers[j])
{
Console.WriteLine("Duplicate Found");
current = rNumber.Next(1, 50);
j = 0; // reset the index iterator
}
}//inner for
numbers[i] = current; // Store the unique random integer
}//outer for
I presume you are looking for random numbers, so the other answer is not what you are looking for.
There are a couple of issues here.
The inner loop is testing for duplicates. However, it is looking from 0 through the end of the array since it is using numbers.length. This should probably be i, to compare with already set values. numbers.length is always 7 regardless of whether or not you set any of the elements.
the assignment is using j, so presuming the first element is not a duplicate, it will be overwritten each time. That should be numbers[i] = current;. No ++ necessary as the for is handling the incrementing.
if you determine that a number is a duplicate, j should be reset to zer to check against the entire list again rather than having the while in the middle.
Without a complete rewrite, the changes will look something like this:
for (int i=1;i<7;i++)
{
current = rNumber.Next(1, 50);
for (int j = 0; j < i; j++) //----------------- loop through set values
{
if (current == numbers[j])
{
Console.WriteLine("Duplicate Found");
current = rNumber.Next(1, 50);
j = 0; // -----------------------reset the counter to start over
}
}//inner for
// if we got here there is no duplicate --------------------------------
numbers[i] = current;
}//outer for
(Please note that I have not tested this code, just added the changes)
you keep overwriting the same indexes in the else, and also checking too many indices causing the first to show up as a duplicate at all times which was false...
change it to:
for (int i=1;i<7;i++)
{
current = rNumber.Next(1, 50);
for (int j = 0; j < i; j++) ///< change to j < i. no need to check the others
{
do
{
if (current == numbers[j])
{
Console.WriteLine("Duplicate Found");
current = rNumber.Next(1, 50);
}
else
{
numbers[i] = current; ///< not j++ but i to prevent writing at the same locations over and over again
break;
}
}while (current == numbers[j]);
}//inner for
}//outer for
What about this?
int[] list = new int[7];
var rn = new Random(Environment.TickCount);
for (int i = 0; i < 7; i++)
{
var next = rn.Next(1, 50);
while(Contains(list, next))
{
next = rn.Next(1, 50);
}
list[i] = next;
}
private bool Contains(IEnumerable<int> ints, int num)
{
foreach(var i in ints)
{
if(i = num) return true;
}
return false;
}

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