How can i find out an array is empty or not, without looping?!
is there any method or anything else?
I mean, in some code like this:
string[] names = new string[5];
names[0] = "Scott";
names[1] = "jack";
names[2] = null;
names[3] = "Jones";
names[4] = "Mesut";
// or
int[] nums = new int[4];
nums[0] = 1;
// nums[1] = 2;
nums[2] = 3;
nums[3] = 4;
or some code like this:
using System;
class Example
{
static void Main()
{
int size = 10;
int counter;
string[] str = new string[size];
for (counter = 0; counter < size; counter++)
{
str[counter] = "A" + counter;
}
str[3] = null;
if (counter == size)
Console.WriteLine("Our array is full!");
if(counter < size)
Console.WriteLine("Our array is not full");
for (int i = 0; i < size; i++)
{
Console.WriteLine(str[i]);
}
}
}
is there anything else for detecting an empty array without looping?
An array just contains a number of elements. There's no concept of an array being "empty" just because each element happens to contain the default value (0, null, or whatever).
If you want a dynamically sized collection, you should use something like List<T> instead of an array.
If you want to detect whether any element of a collection (whether that's a list, an array or anything else) is a non-default value, you have to do that via looping. (You don't have to loop in your source code, but there'll be looping involved somewhere...)
There is no other way than looping through, even LINQ also does the looping automatically.
Instead, use a list<> and check if (listName!=null && listName.Length!=0)
Hope it helps :)
You can use LINQ for that, to check if any element is empty in the array you just can do:
var hasNulls = myArray.Any( a => a == null );
Or if you want to select the ones with values:
var notNulls = myArray.Where( a => a != null );
Related
Imagine i have 2 lists filled with values. I want all the elements from the first list, written into the first column, all the elements from the second list written into the second column and so on.
If both list have the same size, this works fine:
for (int i = 0; i < valueArray.Count(); i++)
{
var newLine = string.Format("{0},{1}", valueArray.ElementAt(i), secondValueArray.ElementAt(i));
sw.Write(newLine);
}
My problem is that if the lists have different sizes, code fails with out of range exception obviously. I tried adding ',' between columns but it's not working.
Instead of ElementAt you should use ElementAtOrDefault :
According to msdn it
Returns the element at a specified index in a sequence or a default
value if the index is out of range.
try this :
List<int?> valueArray = new List<int?>();
List<int?> secondValueArray = new List<int?>();
//... fill lists
valueArray.Add( 1 );
valueArray.Add(2);
valueArray.Add(3);
secondValueArray.Add( 4 );
while (valueArray.Count > secondValueArray.Count)
secondValueArray.Add(null);
while (secondValueArray.Count > valueArray.Count)
valueArray.Add(null);
for (int i = 0; i < valueArray.Count(); i++)
{
var newLine = string.Format("{0},{1}", valueArray.ElementAt(i), secondValueArray.ElementAt(i));
Console.WriteLine(newLine);
}
;
Result :
1,4
2,
3,
As mentioned before, use ElementAtOrDefault(). And check which array is the longest one. Furthermore, you might want to write an empty string instead of NULL if there's no value.
int count = Math.Max(firstArray.Count(), secondArray.Count());
for (int i = 0; i < count; i++)
{
var value1 = firstArray.ElementAtOrDefault(i) ?? String.Empty;
var value2 = secondArray.ElementAtOrDefault(i) ?? String.Empty;
var newLine = string.Format("{0},{1}", value1, value2);
sw.Write(newLine);
}
I'm not sure if this has been asked before but I couldn't see it anywhere.
Can you loop an array? For example:
string[] = array1;
int num1 = 1;
do
{
lbl1.Text = array1[0]
}while(num1 = 1);
How can I make it so it adds one to the element every loop.
I agree that you need to better explain what you're trying to accomplish. If you hardcode num1 then perform a while num1 is equal to its initial value without ever modifying it, you're going to have an indefinite loop. In your example, it will just keep overwriting lbl1 to display the first item in your array.
By "add one to the element every loop", do you mean add each item in the array to your label? Try something like...
foreach (string item in array1)
{
lbl1.Text += array1[item];
}
Otherwise, please provide further details on what you're looking for.
It is really not clear what You want to achieve, but maybe this will get You nearer to the goal:
int[] array1 = new [] {0};
int num1 = 1;
do {
lbl1.Text = (array1[0]++).ToString();
num1++;
} while (num1 < 9);
or
int[] array1 = new [] {0};
for (int i = 0; i < 9; i++) {
lbl1.Text = (array1[0]++).ToString();
}
Not sure what you are trying to accomplish but the following is a stab at a solution
private static void foo(string[] array1)
{
if (array1 != null && array1.Length > 0)
{
for (int num1 = 0; num1 < array1.Length; num1++)
{
string doSomethingWithArrayElement = array1[num1];
}
}
}
I have a comma delimited text file that contains 20 digits separated by commas. These numbers represent earned points and possible points for ten different assignments. We're to use these to calculate a final score for the course.
Normally, I'd iterate through the numbers, creating two sums, divide and be done with it. However, our assignment dictates that we load the list of numbers into two arrays.
so this:
10,10,20,20,30,35,40,50,45,50,45,50,50,50,20,20,45,90,85,85
becomes this:
int[10] earned = {10,20,30,40,45,50,20,45,85};
int[10] possible = {10,20,35,50,50,50,20,90,85};
Right now, I'm using
for (x=0;x<10;x++)
{
earned[x] = scores[x*2]
poss [x] = scores[(x*2)+1]
}
which gives me the results I want, but seems excessively clunky.
Is there a better way?
The following should split each alternating item the list into the other two lists.
int[20] scores = {10,10,20,20,30,35,40,50,45,50,45,50,50,50,20,20,45,90,85,85};
int[10] earned;
int[10] possible;
int a = 0;
for(int x=0; x<10; x++)
{
earned[x] = scores[a++];
possible[x] = scores[a++];
}
You can use LINQ here:
var arrays = csv.Split(',')
.Select((v, index) => new {Value = int.Parse(v), Index = index})
.GroupBy(g => g.Index % 2,
g => g.Value,
(key, values) => values.ToArray())
.ToList();
and then
var earned = arrays[0];
var possible = arrays[1];
Get rid of the "magic" multiplications and illegible array index computations.
var earned = new List<int>();
var possible = new List<int>();
for (x=0; x<scores.Length; x += 2)
{
earned.Add(scores[x + 0]);
possible.Add(scores[x + 1]);
}
This has very little that would need a text comment. This is the gold standard for self-documenting code.
I initially thought the question was a C question because of all the incomprehensible indexing. It looked like pointer magic. It was too clever.
In my codebases I usually have an AsChunked extension available that splits a list into chunks of the given size.
var earned = new List<int>();
var possible = new List<int>();
foreach (var pair in scores.AsChunked(2)) {
earned.Add(pair[0]);
possible.Add(pair[1]);
}
Now the meaning of the code is apparent. The magic is gone.
Even shorter:
var pairs = scores.AsChunked(2);
var earned = pairs.Select(x => x[0]).ToArray();
var possible = pairs.Select(x => x[1]).ToArray();
I suppose you could do it like this:
int[] earned = new int[10];
int[] possible = new int[10];
int resultIndex = 0;
for (int i = 0; i < scores.Count; i = i + 2)
{
earned[resultIndex] = scores[i];
possible[resultIndex] = scores[i + 1];
resultIndex++;
}
You would have to be sure that an equal number of values are stored in scores.
I would leave your code as is. You are technically expressing very directly what your intent is, every 2nd element goes into each array.
The only way to improve that solution is to comment why you are multiplying. But I would expect someone to quickly recognize the trick, or easily reproduce what it is doing. Here is an excessive example of how to comment it. I wouldn't recommend using this directly.
for (x=0;x<10;x++)
{
//scores contains the elements inline one after the other
earned[x] = scores[x*2] //Get the even elements into earned
poss [x] = scores[(x*2)+1] //And the odd into poss
}
However if you really don't like the multiplication, you can track the scores index separately.
int i = 0;
for (int x = 0; x < 10; x++)
{
earned[x] = scores[i++];
poss [x] = scores[i++];
}
But I would probably prefer your version since it does not depend on the order of the operations.
var res = grades.Select((x, i) => new {x,i}).ToLookup(y=>y.i%2, y=>y.x)
int[] earned = res[0].ToArray();
int[] possible = res[1].ToArray();
This will group all grades into two buckets based on index, then you can just do ToArray if you need result in array form.
here is an example of my comment so you do not need to change the code regardless of the list size:
ArrayList Test = new ArrayList { "10,10,20,20,30,35,40,50,45,50,45,50,50,50,20,20,45,90,85,85" };
int[] earned = new int[Test.Count / 2];
int[] Score = new int[Test.Count / 2];
int Counter = 1; // start at one so earned is the first array entered in to
foreach (string TestRow in Test)
{
if (Counter % 2 != 0) // is the counter even
{
int nextNumber = 0;
for (int i = 0; i < Score.Length; i++) // this gets the posistion for the next array entry
{
if (String.IsNullOrEmpty(Convert.ToString(Score[i])))
{
nextNumber = i;
break;
}
}
Score[nextNumber] = Convert.ToInt32(TestRow);
}
else
{
int nextNumber = 0;
for (int i = 0; i < earned.Length; i++) // this gets the posistion for the next array entry
{
if (String.IsNullOrEmpty(Convert.ToString(earned[i])))
{
nextNumber = i;
break;
}
}
earned[nextNumber] = Convert.ToInt32(TestRow);
}
Counter++
}
I would like to programmatically add or remove some elements to a string array in C#, but still keeping the items I had before, a bit like the VB function ReDim Preserve.
The obvious suggestion would be to use a List<string> instead, which you will have already read from the other answers. This is definitely the best way in a real development scenario.
Of course, I want to make things more interesting (my day that is), so I will answer your question directly.
Here are a couple of functions that will Add and Remove elements from a string[]...
string[] Add(string[] array, string newValue){
int newLength = array.Length + 1;
string[] result = new string[newLength];
for(int i = 0; i < array.Length; i++)
result[i] = array[i];
result[newLength -1] = newValue;
return result;
}
string[] RemoveAt(string[] array, int index){
int newLength = array.Length - 1;
if(newLength < 1)
{
return array;//probably want to do some better logic for removing the last element
}
//this would also be a good time to check for "index out of bounds" and throw an exception or handle some other way
string[] result = new string[newLength];
int newCounter = 0;
for(int i = 0; i < array.Length; i++)
{
if(i == index)//it is assumed at this point i will match index once only
{
continue;
}
result[newCounter] = array[i];
newCounter++;
}
return result;
}
If you really won't (or can't) use a generic collection instead of your array, Array.Resize is c#'s version of redim preserve:
var oldA = new [] {1,2,3,4};
Array.Resize(ref oldA,10);
foreach(var i in oldA) Console.WriteLine(i); //1 2 3 4 0 0 0 0 0 0
Don't use an array - use a generic List<T> which allows you to add items dynamically.
If this is not an option, you can use Array.Copy or Array.CopyTo to copy the array into a larger array.
Since arrays implement IEnumerable<T> you can use Concat:
string[] strArr = { "foo", "bar" };
strArr = strArr.Concat(new string[] { "something", "new" });
Or what would be more appropriate would be to use a collection type that supports inline manipulation.
Use List<string> instead of string[].
List allows you to add and remove items with good performance.
What's abaut this one:
List<int> tmpList = intArry.ToList();
tmpList.Add(anyInt);
intArry = tmpList.ToArray();
One liner:
string[] items = new string[] { "a", "b" };
// this adds "c" to the string array:
items = new List<string>(items) { "c" }.ToArray();
You should take a look at the List object. Lists tend to be better at changing dynamically like you want. Arrays not so much...
You can use a generic collection, like List<>
List<string> list = new List<string>();
// add
list.Add("element");
// remove
list.Remove("element");
You can use this snippet:
static void Main(string[] args)
{
Console.WriteLine("Enter number:");
int fnum = 0;
bool chek = Int32.TryParse(Console.ReadLine(),out fnum);
Console.WriteLine("Enter number:");
int snum = 0;
chek = Int32.TryParse(Console.ReadLine(),out snum);
Console.WriteLine("Enter number:");
int thnum = 0;
chek = Int32.TryParse(Console.ReadLine(),out thnum);
int[] arr = AddToArr(fnum,snum,thnum);
IOrderedEnumerable<int> oarr = arr.OrderBy(delegate(int s)
{
return s;
});
Console.WriteLine("Here your result:");
oarr.ToList().FindAll(delegate(int num) {
Console.WriteLine(num);
return num > 0;
});
}
public static int[] AddToArr(params int[] arr) {
return arr;
}
I hope this will help to you, just change the type
How can I define a dynamic array in C#?
C# doesn't provide dynamic arrays. Instead, it offers List class which works the same way.
To use lists, write at the top of your file:
using System.Collections.Generic;
And where you want to make use of a list, write (example for strings):
List<string> mylist = new List<string>();
mylist.Add("First string in list");
Take a look at Array.Resize if you need to resize an array.
// Create and initialize a new string array.
String[] myArr = {"The", "quick", "brown", "fox", "jumps",
"over", "the", "lazy", "dog"};
// Resize the array to a bigger size (five elements larger).
Array.Resize(ref myArr, myArr.Length + 5);
// Resize the array to a smaller size (four elements).
Array.Resize(ref myArr, 4);
Alternatively you could use the List class as others have mentioned. Make sure you specify an initial size if you know it ahead of time to keep the list from having to resize itself underneath. See the remarks section of the initial size link.
List<string> dinosaurs = new List<string>(4);
Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity);
dinosaurs.Add("Tyrannosaurus");
dinosaurs.Add("Amargasaurus");
dinosaurs.Add("Mamenchisaurus");
dinosaurs.Add("Deinonychus");
If you need the array from the List, you can use the ToArray() function on the list.
string[] dinos = dinosaurs.ToArray();
C# does provide dynamic arrays and dynamic array manipulation. The base of an array is dynamic and can be modified with a variable. You can find the array tutorial here (https://msdn.microsoft.com/en-us/library/aa288453%28v=vs.71%29.aspx). I have also included code that demonstrates an empty set array and a dynamic array that can be resized at run time.
class Program
{
static void Main(string[] args)
{
int x = Convert.ToInt32(Console.ReadLine());
int y = Convert.ToInt32(Console.ReadLine());
Console.WriteLine(x);
{
int[] dynamicArray1 = { };//empty array
int[] numbers;//another way to declare a variable array as all arrays start as variable size
numbers = new int[x];//setting this array to an unknown variable (will be user input)
for (int tmpInt = 0; tmpInt < x; tmpInt++)//build up the first variable array (numbers)
{
numbers[tmpInt] = tmpInt;
}
Array.Resize(ref numbers,y);// resize to variable input
dynamicArray1 = numbers;//set the empty set array to the numbers array size
for (int z = 0; z < y; z++)//print to the new resize
{
Console.WriteLine(numbers[z].ToString());//print the numbers value
Console.WriteLine(dynamicArray1[z].ToString());//print the empty set value
}
}
Console.Write("Dynamic Arrays ");
var name = Console.ReadLine();
}
}
Actually you can have Dynamic Arrays in C# it's very simple.
keep in mind that the response to your question above is also correct you could declare a
List Generic
The way to Create a Dynamic Array would be to declare your Array for example
string[] dynamicArry1 = { };//notice I did not declare a size for the array
List<String> tmpList = new List<string>();
int i = 1;
for(int tmpInt = 0; tmpInt < 5; tmpInt++)
{
tmpList.Add("Testing, 1.0." + tmpInt + ", 200, 3.4" + tmpInt +"," + DateTime.Now.ToShortDateString());
//dynamicArry1[tmpInt] = new string[] { tmpList[tmpInt].ToCharArray() };
}
dynamicArry1 = tmpList.ToArray();
how about ArrayList ?
If I'm not wrong ArrayList is an implementation of dynamic arrays
Example of Defining Dynamic Array in C#:
Console.WriteLine("Define Array Size? ");
int number = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Enter numbers:\n");
int[] arr = new int[number];
for (int i = 0; i < number; i++)
{
arr[i] = Convert.ToInt32(Console.ReadLine());
}
for (int i = 0; i < arr.Length; i++ )
{
Console.WriteLine("Array Index: "+i + " AND Array Item: " + arr[i].ToString());
}
Console.ReadKey();
like so
int nSize = 17;
int[] arrn = new int[nSize];
nSize++;
arrn = new int[nSize];