I have the following code which generates two non-duplicates arrays of integers based on a ratio. The codes works perfectly but for a 4000 line file, this takes some time.
//Train & Test numbers
int train = (int)(((double)Settings.Default.TrainingRatio / 100) * inputLines.Count());
int test = inputLines.Count() - train;
//Train & Test list
Random rnd = new Random();
var trainList = Enumerable.Range(1, inputLines.Count()).OrderBy(x => rnd.Next()).Take(train).ToList();
var testList = new List<int>();
for (int i = 1; i <= inputLines.Count(); i++)
{
if (!trainList.Contains(i))
testList.Add(i);
}
And even worse, this is how i read those lines:
foreach (var n in trainList)
{
objDataintilizer.GenerateMasterLableFile(inputLines.Skip(n - 1).Take(1).First().ToString());
}
Could anyone advice another way that could have a better performance.
Each time your code calls inputFiles.Count(), you're effectively re-reading the entire file, since File.ReadLines is using deferred execution, and you aren't materializing it. Since you need the entire list in-memory anyway, use File.ReadAllLines instead, which returns a string[] and has a Length property, which is an O(1) operation instead of O(N).
Then, instead of using a List<int> for your trainList, use a HashSet<int> which will be faster to lookup with Contains:
public static class EnumerableExtensions
{
public static HashSet<T> ToHashSet(this IEnumerable<T> enumerable)
{
return new HashSet<T>(enumerable);
}
}
Random rnd = new Random();
var trainList = Enumerable.Range(1, inputLines.Length)
.OrderBy(x => rnd.Next())
.Take(train)
.ToHashSet();
var testList = new List<int>();
for (int i = 1; i <= inputLines.Length; i++)
{
if (!trainList.Contains(i))
testList.Add(i);
}
I am using an extension method which shuffles a generic list. This works
public static void Shuffle<T>(this IList<T> list)
{
RNGCryptoServiceProvider provider = new RNGCryptoServiceProvider();
int n = list.Count;
while (n > 1)
{
byte[] box = new byte[1];
do provider.GetBytes(box);
while (!(box[0] < n * (Byte.MaxValue / n)));
int k = (box[0] % n);
n--;
T value = list[k];
list[k] = list[n];
list[n] = value;
}
}
I am trying trying to create another extension method which would utilize Shuffle(), but would shuffle the items in a list in groups based on a defined group size. This method seems to work when debugging the extension method, but the source list in the calling code still contains the original list after the extension call:
public static void GroupRandomize<T>(this IList<T> sourceList, int groupSize)
{
List<T> shuffledList = new List<T>();
List<T> tempList = new List<T>();
int addCounter = 0;
for (int i = 0; i < sourceList.Count; i++)
{
tempList.Add(sourceList[i]);
// if we've built a full group, or we're done processing the entire list
if ((addCounter == groupSize - 1) || (i == sourceList.Count - 1))
{
tempList.Shuffle();
shuffledList.AddRange(tempList);
tempList.Clear();
addCounter = 0;
}
else
{
addCounter++;
}
}
sourceList = shuffledList;
}
How do I ensure the shuffled list is stored properly into the source list?
sourceList is actually a local variable.
Might be better to return shuffedList;
var newList = caller.GroupRandomize<T>(5) ;
sourceList = shuffledList;
This will do nothing unless you are using a ref parameter. You could change your method so that it modifies the sourceList directly:
for(int i = 0; i < sourceList.Length; i++)
sourceList[i] = shuffledList[i];
But I'd recommend changing your approach so that the extension methods return new, shuffled lists, leaving the original lists intact. So instead of:
var list = GetList();
list.Shuffle();
... you would say:
var list = GetList().Shuffle();
Make it a regular method instead of an extension so you can pass it in by reference:
public static void GroupRandomize<T>(ref IList<T> sourceList, int groupSize) {
// ... stuff
sourceList = shuffledList;
}
Or if you don't want to change the header of the method, you could do the something like:
sourceList.Clear();
sourceList.AddRange( shuffledList );
Edit:
As stated by bperniciaro, The AddRange method is not available in the IList<T> interface.
StriplingWarrior already suggested an implementation that does what AddRange would do, so instead I will just improve his answer a little by pointing to another answer, by hvostt, that implements AddRange as an extension method of IList<T>.
I have the following method that sorts a list of binding source indices and puts their corresponding objects into an array. I have also tried using Array.Sort() and neither works, the code within the foreach loop never gets called. I have tested that the variable int[] indices is neither empty nor null.
internal void Foo(int[] indices)
{
var bar = new Object[indices.length];
int i = 0;
foreach (int index in indices.OrderBy(x => x))
{
// this block never gets called
bar[i] = BindingSource[index];
i++;
}
}
You can try this:
var bar = indices.OrderBy(x => x).Select(x => BindingSource[x]).ToArray();
But I think that your code should work though I think that you could improve it using a for-loop instead of a foreach.
internal void Foo(int[] indices)
{
var bar = new Object[indices.Length];
indices = indices.OrderBy(x => x);
for(int i = 0; i < indices.Length; i++)
bar[i] = BindingSource[indices[i]];
}
Another thing, you should get sure that the indices.Length doesn't equal 0 so I think that indices is empty.
PS : C# is case-sensitive so indices.length in your code should be indices.Length .
The issue is that OrderBy was not returning the sorted array, as I had assumed it did. The following is my solution.
internal void Foo(int[] indices)
{
var bar = new Object[indices.Length];
int i = 0;
indices = indices.OrderBy(x => x).ToArray();
foreach (int index in indices)
{
// now this block gets called
bar[i] = BindingSource[index];
i++;
}
}
I want to create array 10 * 10 * 10 in C# like int[][][] (not int[,,]).
I can write code:
int[][][] count = new int[10][][];
for (int i = 0; i < 10; i++)
{
count[i] = new int[10][];
for (int j = 0; j < 10; j++)
count[i][j] = new int[10];
}
but I am looking for a more beautiful way for it. May be something like that:
int[][][] count = new int[10][10][10];
int[][][] my3DArray = CreateJaggedArray<int[][][]>(1, 2, 3);
using
static T CreateJaggedArray<T>(params int[] lengths)
{
return (T)InitializeJaggedArray(typeof(T).GetElementType(), 0, lengths);
}
static object InitializeJaggedArray(Type type, int index, int[] lengths)
{
Array array = Array.CreateInstance(type, lengths[index]);
Type elementType = type.GetElementType();
if (elementType != null)
{
for (int i = 0; i < lengths[index]; i++)
{
array.SetValue(
InitializeJaggedArray(elementType, index + 1, lengths), i);
}
}
return array;
}
You could try this:
int[][][] data =
{
new[]
{
new[] {1,2,3}
},
new[]
{
new[] {1,2,3}
}
};
Or with no explicit values:
int[][][] data =
{
new[]
{
Enumerable.Range(1, 100).ToArray()
},
new[]
{
Enumerable.Range(2, 100).ToArray()
}
};
There is no built in way to create an array and create all elements in it, so it's not going to be even close to how simple you would want it to be. It's going to be as much work as it really is.
You can make a method for creating an array and all objects in it:
public static T[] CreateArray<T>(int cnt, Func<T> itemCreator) {
T[] result = new T[cnt];
for (int i = 0; i < result.Length; i++) {
result[i] = itemCreator();
}
return result;
}
Then you can use that to create a three level jagged array:
int[][][] count = CreateArray<int[][]>(10, () => CreateArray<int[]>(10, () => new int[10]));
With a little help from Linq
int[][][] count = new int[10].Select(x => new int[10].Select(x => new int[10]).ToArray()).ToArray();
It sure isn't pretty and probably not fast but it's a one-liner.
There is no 'more elegant' way than writing the 2 for-loops. That is why they are called 'jagged', the sizes of each sub-array can vary.
But that leaves the question: why not use the [,,] version?
int[][][] count = Array.ConvertAll(new bool[10], x =>
Array.ConvertAll(new bool[10], y => new int[10]));
A three dimensional array sounds like a good case for creating your own Class. Being object oriented can be beautiful.
You could use a dataset with identical datatables. That could behave like a 3D object (xyz = row, column, table)... But you're going to end up with something big no matter what you do; you still have to account for 1000 items.
Why don't you try this?
int[,,] count = new int[10, 10, 10]; // Multi-dimentional array.
Any problem you see with this kind of representation??
Probably a really simple one this - I'm starting out with C# and need to add values to an array, for example:
int[] terms;
for(int runs = 0; runs < 400; runs++)
{
terms[] = runs;
}
For those who have used PHP, here's what I'm trying to do in C#:
$arr = array();
for ($i = 0; $i < 10; $i++) {
$arr[] = $i;
}
You can do this way -
int[] terms = new int[400];
for (int runs = 0; runs < 400; runs++)
{
terms[runs] = value;
}
Alternatively, you can use Lists - the advantage with lists being, you don't need to know the array size when instantiating the list.
List<int> termsList = new List<int>();
for (int runs = 0; runs < 400; runs++)
{
termsList.Add(value);
}
// You can convert it back to an array if you would like to
int[] terms = termsList.ToArray();
Edit: a) for loops on List<T> are a bit more than 2 times cheaper than foreach loops on List<T>, b) Looping on array is around 2 times cheaper than looping on List<T>, c) looping on array using for is 5 times cheaper than looping on List<T> using foreach (which most of us do).
Using Linq's method Concat makes this simple
int[] array = new int[] { 3, 4 };
array = array.Concat(new int[] { 2 }).ToArray();
result
3,4,2
If you're writing in C# 3, you can do it with a one-liner:
int[] terms = Enumerable.Range(0, 400).ToArray();
This code snippet assumes that you have a using directive for System.Linq at the top of your file.
On the other hand, if you're looking for something that can be dynamically resized, as it appears is the case for PHP (I've never actually learned it), then you may want to use a List instead of an int[]. Here's what that code would look like:
List<int> terms = Enumerable.Range(0, 400).ToList();
Note, however, that you cannot simply add a 401st element by setting terms[400] to a value. You'd instead need to call Add() like this:
terms.Add(1337);
By 2019 you can use Append, Prepend using LinQ in just one line
using System.Linq;
and then in NET 6.0:
terms = terms.Append(21);
or versions lower than NET 6.0
terms = terms.Append(21).ToArray();
Answers on how to do it using an array are provided here.
However, C# has a very handy thing called System.Collections
Collections are fancy alternatives to using an array, though many of them use an array internally.
For example, C# has a collection called List that functions very similar to the PHP array.
using System.Collections.Generic;
// Create a List, and it can only contain integers.
List<int> list = new List<int>();
for (int i = 0; i < 400; i++)
{
list.Add(i);
}
Using a List as an intermediary is the easiest way, as others have described, but since your input is an array and you don't just want to keep the data in a List, I presume you might be concerned about performance.
The most efficient method is likely allocating a new array and then using Array.Copy or Array.CopyTo. This is not hard if you just want to add an item to the end of the list:
public static T[] Add<T>(this T[] target, T item)
{
if (target == null)
{
//TODO: Return null or throw ArgumentNullException;
}
T[] result = new T[target.Length + 1];
target.CopyTo(result, 0);
result[target.Length] = item;
return result;
}
I can also post code for an Insert extension method that takes a destination index as input, if desired. It's a little more complicated and uses the static method Array.Copy 1-2 times.
Based on the answer of Thracx (I don't have enough points to answer):
public static T[] Add<T>(this T[] target, params T[] items)
{
// Validate the parameters
if (target == null) {
target = new T[] { };
}
if (items== null) {
items = new T[] { };
}
// Join the arrays
T[] result = new T[target.Length + items.Length];
target.CopyTo(result, 0);
items.CopyTo(result, target.Length);
return result;
}
This allows to add more than just one item to the array, or just pass an array as a parameter to join two arrays.
You have to allocate the array first:
int [] terms = new int[400]; // allocate an array of 400 ints
for(int runs = 0; runs < terms.Length; runs++) // Use Length property rather than the 400 magic number again
{
terms[runs] = value;
}
int ArraySize = 400;
int[] terms = new int[ArraySize];
for(int runs = 0; runs < ArraySize; runs++)
{
terms[runs] = runs;
}
That would be how I'd code it.
C# arrays are fixed length and always indexed. Go with Motti's solution:
int [] terms = new int[400];
for(int runs = 0; runs < 400; runs++)
{
terms[runs] = value;
}
Note that this array is a dense array, a contiguous block of 400 bytes where you can drop things. If you want a dynamically sized array, use a List<int>.
List<int> terms = new List<int>();
for(int runs = 0; runs < 400; runs ++)
{
terms.Add(runs);
}
Neither int[] nor List<int> is an associative array -- that would be a Dictionary<> in C#. Both arrays and lists are dense.
You can't just add an element to an array easily. You can set the element at a given position as fallen888 outlined, but I recommend to use a List<int> or a Collection<int> instead, and use ToArray() if you need it converted into an array.
If you really need an array the following is probly the simplest:
using System.Collections.Generic;
// Create a List, and it can only contain integers.
List<int> list = new List<int>();
for (int i = 0; i < 400; i++)
{
list.Add(i);
}
int [] terms = list.ToArray();
one approach is to fill an array via LINQ
if you want to fill an array with one element
you can simply write
string[] arrayToBeFilled;
arrayToBeFilled= arrayToBeFilled.Append("str").ToArray();
furthermore, If you want to fill an array with multiple elements you can use the
previous code in a loop
//the array you want to fill values in
string[] arrayToBeFilled;
//list of values that you want to fill inside an array
List<string> listToFill = new List<string> { "a1", "a2", "a3" };
//looping through list to start filling the array
foreach (string str in listToFill){
// here are the LINQ extensions
arrayToBeFilled= arrayToBeFilled.Append(str).ToArray();
}
Array Push Example
public void ArrayPush<T>(ref T[] table, object value)
{
Array.Resize(ref table, table.Length + 1); // Resizing the array for the cloned length (+-) (+1)
table.SetValue(value, table.Length - 1); // Setting the value for the new element
}
int[] terms = new int[10]; //create 10 empty index in array terms
//fill value = 400 for every index (run) in the array
//terms.Length is the total length of the array, it is equal to 10 in this case
for (int run = 0; run < terms.Length; run++)
{
terms[run] = 400;
}
//print value from each of the index
for (int run = 0; run < terms.Length; run++)
{
Console.WriteLine("Value in index {0}:\t{1}",run, terms[run]);
}
Console.ReadLine();
/*Output：
Value in index 0: 400
Value in index 1: 400
Value in index 2: 400
Value in index 3: 400
Value in index 4: 400
Value in index 5: 400
Value in index 6: 400
Value in index 7: 400
Value in index 8: 400
Value in index 9: 400
*/
If you don't know the size of the Array or already have an existing array that you are adding to. You can go about this in two ways. The first is using a generic List<T>:
To do this you will want convert the array to a var termsList = terms.ToList(); and use the Add method. Then when done use the var terms = termsList.ToArray(); method to convert back to an array.
var terms = default(int[]);
var termsList = terms == null ? new List<int>() : terms.ToList();
for(var i = 0; i < 400; i++)
termsList.Add(i);
terms = termsList.ToArray();
The second way is resizing the current array:
var terms = default(int[]);
for(var i = 0; i < 400; i++)
{
if(terms == null)
terms = new int[1];
else
Array.Resize<int>(ref terms, terms.Length + 1);
terms[terms.Length - 1] = i;
}
If you are using .NET 3.5 Array.Add(...);
Both of these will allow you to do it dynamically. If you will be adding lots of items then just use a List<T>. If it's just a couple of items then it will have better performance resizing the array. This is because you take more of a hit for creating the List<T> object.
Times in ticks:
3 items
Array Resize Time: 6
List Add Time: 16
400 items
Array Resize Time: 305
List Add Time: 20
I will add this for a another variant. I prefer this type of functional coding lines more.
Enumerable.Range(0, 400).Select(x => x).ToArray();
You can't do this directly. However, you can use Linq to do this:
List<int> termsLst=new List<int>();
for (int runs = 0; runs < 400; runs++)
{
termsLst.Add(runs);
}
int[] terms = termsLst.ToArray();
If the array terms wasn't empty in the beginning, you can convert it to List first then do your stuf. Like:
List<int> termsLst = terms.ToList();
for (int runs = 0; runs < 400; runs++)
{
termsLst.Add(runs);
}
terms = termsLst.ToArray();
Note: don't miss adding 'using System.Linq;' at the begaining of the file.
This seems like a lot less trouble to me:
var usageList = usageArray.ToList();
usageList.Add("newstuff");
usageArray = usageList.ToArray();
Just a different approach:
int runs = 0;
bool batting = true;
string scorecard;
while (batting = runs < 400)
scorecard += "!" + runs++;
return scorecard.Split("!");
int[] terms = new int[400];
for(int runs = 0; runs < 400; runs++)
{
terms[runs] = value;
}
static void Main(string[] args)
{
int[] arrayname = new int[5];/*arrayname is an array of 5 integer [5] mean in array [0],[1],[2],[3],[4],[5] because array starts with zero*/
int i, j;
/*initialize elements of array arrayname*/
for (i = 0; i < 5; i++)
{
arrayname[i] = i + 100;
}
/*output each array element value*/
for (j = 0; j < 5; j++)
{
Console.WriteLine("Element and output value [{0}]={1}",j,arrayname[j]);
}
Console.ReadKey();/*Obtains the next character or function key pressed by the user.
The pressed key is displayed in the console window.*/
}
/*arrayname is an array of 5 integer*/
int[] arrayname = new int[5];
int i, j;
/*initialize elements of array arrayname*/
for (i = 0; i < 5; i++)
{
arrayname[i] = i + 100;
}
To add the list values to string array using C# without using ToArray() method
List<string> list = new List<string>();
list.Add("one");
list.Add("two");
list.Add("three");
list.Add("four");
list.Add("five");
string[] values = new string[list.Count];//assigning the count for array
for(int i=0;i<list.Count;i++)
{
values[i] = list[i].ToString();
}
Output of the value array contains:
one
two
three
four
five
You can do this is with a list. here is how
List<string> info = new List<string>();
info.Add("finally worked");
and if you need to return this array do
return info.ToArray();
Here is one way how to deal with adding new numbers and strings to Array:
int[] ids = new int[10];
ids[0] = 1;
string[] names = new string[10];
do
{
for (int i = 0; i < names.Length; i++)
{
Console.WriteLine("Enter Name");
names[i] = Convert.ToString(Console.ReadLine());
Console.WriteLine($"The Name is: {names[i]}");
Console.WriteLine($"the index of name is: {i}");
Console.WriteLine("Enter ID");
ids[i] = Convert.ToInt32(Console.ReadLine());
Console.WriteLine($"The number is: {ids[i]}");
Console.WriteLine($"the index is: {i}");
}
} while (names.Length <= 10);