Related
Sorry if this is a duplicate, first question here...
I wanna operate on a large array of structs called notes.
But I don't wanna operate on every element of notes. I'm trying to use a filter of an int array (int[]) as to skip quite a few of it as shown in below code.
Note[] notes = new Note[]
{
// Struct stuff ...
};
int[] filter = new int[]{ 4,20,50,367... };
for (int i = 0; i < notes.Length; i++)
{
bool flag = false;
for (int j = 0; j < filter.Length; j++)
{
if (i == filter[j])
{
flag = true;
break;
}
}
if (flag) continue;
// Do something on notes[i]
}
The problem is, the code will run really slow (I think) when both notes array and filter array expands.
So, is there a better and faster way to do this? Note that the size of filter can be anything based on other conditions
We can get rid of inner loop with a help of HashSet<int> while having a better O(|filter| + |notes|) time complexity instead of initial O(|filter| * |notes|):
Note[] notes = new Note[] {
... //Struct stuff
};
int[] filter = new int[] {
4, 20, 50, 367...
};
HashSet<int> toExclude = new HashSet<int>(filter);
for (int i = 0; i < notes.Length; i++) {
if (toExclude.Contains(i)) // O(1) time complexity
continue;
//Do something on notes[i]
}
You could filter the notes using Linq like this:
Note[] notes = new Note[]{ ...//Struct stuff };
int[] filter = new int[]{ 4,20,50,367... };
var filteredNotes = notes.ToList().Where(note => !filter.Contains(note.Id)).ToList();
foreach(var note in filteredNotes)
{
//Do something on note
}
You would need to test the performance though, as Linq tends to be slow in specific circumstances.
You can loop the filter array and create a new boolean array that has all elements you want to skip as true.
bool[] filterArray= new bool[notes.Length];
foreach(var index in filter)
{
if(index<filterArray.Length)
filterArray[index]=true;
}
Then you have to just check the index of this array.
for (int i = 0; i < notes.Length; i++)
{
if(!filterArray[i]){
//Do something on notes[i]
}
}
The complexity of this code will be O(m+n*X) where m is the length of the filter array, n the length of the node array and X the complexity of your operation on notes[i]. Assuming mO(n*X).
Your complexity now is O(m*n*X)
Now, I may get negative points because perhaps somewhere in vast internet there is already an answer to this but I tried to look for it and I simply couldnt find it.
The gist of the problem is that HackerRanks wants you to create an array with a size decided by the user, then have the user add its values (integers) and finally have the program sum its values.
There are plenty of ways to do it and I already know how to but my problem is that I just can't understand Hackerrank's code sample in C# it gave me. I commented the parts I don't understand, which is most of it:
static int simpleArraySum(int n, int[] ar) {
// Complete this function
int sum = 0;
foreach( var item in ar){
sum += item;
}
return sum;
}
static void Main(String[] args) {
//I know what this does
int n = Convert.ToInt32(Console.ReadLine());
//I am lost here, just why create a string array and add the split method?
string[] ar_temp = Console.ReadLine().Split(' ');
//I dont understand here neither, what is it converting? What is the parse for?
int[] ar = Array.ConvertAll(ar_temp,Int32.Parse);
//Why send the n when all you need is the array itself?
int result = simpleArraySum(n, ar);
Console.WriteLine(result);
}
I know some people hate HackerRank, and honestly, I do too but it does gives me some nice ways to test my limited skills in coding with c# and testing my logic. So, if there are better sites that helps you test your logic as a CS please share them with me.
Here is the code I made to solve this problem in Visual Studio but for some stupid reason Hackerrank wont accept it unless I make custom inputs:
//This code can be potentially shorter using the code commented further below.
//For practice's sake, it was made longer.
static int simpleArraySum(int[] arr_temp)
{
int total = 0;
foreach (var item in arr_temp)
{
total += item;
}
return total;
}
static void Main(String[] args)
{
int n = Convert.ToInt32(Console.ReadLine());
int[] arr_temp = new int[n];
for (int i = 0; i < n; i++)
{
arr_temp[i] = Convert.ToInt32(Console.ReadLine());
}
int result = simpleArraySum(arr_temp);
//int result = arr_temp.Sum();
Console.WriteLine(result);
Console.ReadLine();
}
You need to convert to string array since if you're on the main method, all it gets are string values from the argument list. To get the sum then you need to convert the string into a usable number / integer.
I agree that it doesn't make sense to send the first argument n in simpleArraySum because n is simply unused.
as for the part int[] ar = Array.ConvertAll(ar_temp,Int32.Parse); it simply tries to take in all the integers into the array. It is also risky because if you accidentally pass in a string then it will throw an error i.e. pass in "3 4 1 f" <- f will throw an exception, unless this is the desired behaviour.
Personally I think the main method should not be interested in getting involved too much with the data, the heavy lifting should be done in the methods. The better version perhaps would be to modify simpleArraySum and refactor that line in like:
static int simpleArraySum(string input)
{
String[] fields = input.Split(null);
List<int> vals = new List<int>();
foreach (string i in fields)
{
var j = 0;
if (Int32.TryParse(i, out j)) vals.Add(j);
}
int sum = 0;
foreach (var item in vals)
{
sum += item;
}
return sum;
}
I introduced the use of generic list because it's more readable if not cleaner, although the use of List might look overkill to some programmers and might not be as light weight as just using an array, hence on the other hand you can easily stick to using arrays except that it needs to be initialized with the length i.e. int[] vals = new int[fields.Length]; Roughly:
static int simpleArraySum(string input)
{
String[] fields = input.Split(null);
int[] vals = new int[fields.Length];
for (int i = 0; i < fields.Length; i++)
{
var j = 0;
if (Int32.TryParse(fields[i], out j)) vals[i] = j;
}
int sum = 0;
foreach (var item in vals)
{
sum += item;
}
return sum;
}
here my code i hope that helps
static int simpleArraySum(int[] ar,int count) {
if (count > 0 && count <= 10000)
{
if (count == ar.Length)
{
if (!ar.Any(item => (item < 0 || item >= 10000)))
{
return ar.Sum();
}
}
}
return 0;
}
and in main
int arCount = Convert.ToInt32(Console.ReadLine());
int[] arr = Array.ConvertAll(Console.ReadLine().Split(' '), arTemp => Convert.ToInt32(arTemp));
int result = simpleArraySum(arr, arCount);
Console.WriteLine(result);
since Array.ConvertAll() takes a string and convert it to one type array
int or float for example
For users still looking for a 100% C# solution: In above mentioned coding websites do not modify the main function. The aim of the test is to complete the function via the online complier.
using System.Linq;
public static int simpleArraySum(List<int> ar)
{
int sum = ar.Sum();
return sum;
}
I have a quite short List<int>:
var list = new List<int> {0, 4, 1, 3};
The list is not sorted.
I need to find the lowest integer, starting from 0, which does not belong to the list.
At the moment I use the following algorithm:
int x = 0;
while (list.Contains(x))
x++;
// In this example it must be: x = 2
The algorithm is pretty simple, but it is not linear O(n), and I need to compute this value a huge number of times using different lists.
How can I speed up this method?
Without knowing too much about your actual limitations, maybe this could be a solution:
int breakpoint = 153; // Or whatever number you've found is the breakpoint
int FirstMissingNumber(List<int> list)
IEnumerable<int> toIterateOver = list;
if (list.Count > breakpoint)
toIterateOver = new HashSet<int>(list);
int i = 0;
while (toIterateOver.Contains(i))
i++;
return i;
}
Note though that for smaller lists the overhead of creating the hashset surely is larger than the O(1) speed gain on Contains().
EDIT:
Added a breakpoint "switch", you have to manually find out where the breakpoint is in your environment though.
Why not just sort the list and loop through it to find out the missing number like below
var list = new List<int> { 0, 4, 1, 3 };
list.Sort();
for (int i = 0; i < list.Count; i++)
{
if (!list.Contains(i))
{
Console.WriteLine("Missing {0}", i);
break;
}
}
I have been stumped on this one for a while. I want to take a List and order the list such that the Products with the largest Price end up in the middle of the list. And I also want to do the opposite, i.e. make sure that the items with the largest price end up on the outer boundaries of the list.
Imagine a data structure like this.. 1,2,3,4,5,6,7,8,9,10
In the first scenario I need to get back 1,3,5,7,9,10,8,6,4,2
In the second scenario I need to get back 10,8,6,4,2,1,3,5,7,9
The list may have upwards of 250 items, the numbers will not be evenly distributed, and they will not be sequential, and I wanted to minimize copying. The numbers will be contained in Product objects, and not simple primitive integers.
Is there a simple solution that I am not seeing?
Any thoughts.
So for those of you wondering what I am up to, I am ordering items based on calculated font size. Here is the code that I went with...
The Implementation...
private void Reorder()
{
var tempList = new LinkedList<DisplayTag>();
bool even = true;
foreach (var tag in this) {
if (even)
tempList.AddLast(tag);
else
tempList.AddFirst(tag);
even = !even;
}
this.Clear();
this.AddRange(tempList);
}
The Test...
[TestCase(DisplayTagOrder.SmallestToLargest, Result=new[]{10,14,18,22,26,30})]
[TestCase(DisplayTagOrder.LargestToSmallest, Result=new[]{30,26,22,18,14,10})]
[TestCase(DisplayTagOrder.LargestInTheMiddle, Result = new[] { 10, 18, 26, 30, 22, 14 })]
[TestCase(DisplayTagOrder.LargestOnTheEnds, Result = new[] { 30, 22, 14, 10, 18, 26 })]
public int[] CalculateFontSize_Orders_Tags_Appropriately(DisplayTagOrder sortOrder)
{
list.CloudOrder = sortOrder;
list.CalculateFontSize();
var result = (from displayTag in list select displayTag.FontSize).ToArray();
return result;
}
The Usage...
public void CalculateFontSize()
{
GetMaximumRange();
GetMinimunRange();
CalculateDelta();
this.ForEach((displayTag) => CalculateFontSize(displayTag));
OrderByFontSize();
}
private void OrderByFontSize()
{
switch (CloudOrder) {
case DisplayTagOrder.SmallestToLargest:
this.Sort((arg1, arg2) => arg1.FontSize.CompareTo(arg2.FontSize));
break;
case DisplayTagOrder.LargestToSmallest:
this.Sort(new LargestFirstComparer());
break;
case DisplayTagOrder.LargestInTheMiddle:
this.Sort(new LargestFirstComparer());
Reorder();
break;
case DisplayTagOrder.LargestOnTheEnds:
this.Sort();
Reorder();
break;
}
}
The appropriate data structure is a LinkedList because it allows you to efficiently add to either end:
LinkedList<int> result = new LinkedList<int>();
int[] array = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
Array.Sort(array);
bool odd = true;
foreach (var x in array)
{
if (odd)
result.AddLast(x);
else
result.AddFirst(x);
odd = !odd;
}
foreach (int item in result)
Console.Write("{0} ", item);
No extra copying steps, no reversing steps, ... just a small overhead per node for storage.
C# Iterator version
(Very simple code to satisfy all conditions.)
One function to rule them all! Doesn't use intermediate storage collection (see yield keyword). Orders the large numbers either to the middle, or to the sides depending on the argument. It's implemented as a C# iterator
// Pass forward sorted array for large middle numbers,
// or reverse sorted array for large side numbers.
//
public static IEnumerable<long> CurveOrder(long[] nums) {
if (nums == null || nums.Length == 0)
yield break; // Nothing to do.
// Move forward every two.
for (int i = 0; i < nums.Length; i+=2)
yield return nums[i];
// Move backward every other two. Note: Length%2 makes sure we're on the correct offset.
for (int i = nums.Length-1 - nums.Length%2; i >= 0; i-=2)
yield return nums[i];
}
Example Usage
For example with array long[] nums = { 1,2,3,4,5,6,7,8,9,10,11 };
Start with forward sort order, to bump high numbers into the middle.
Array.Sort(nums); //forward sort
// Array argument will be: { 1,2,3,4,5,6,7,8,9,10,11 };
long[] arrLargeMiddle = CurveOrder(nums).ToArray();
Produces: 1 3 5 7 9 11 10 8 6 4 2
Or, Start with reverse sort order, to push high numbers to sides.
Array.Reverse(nums); //reverse sort
// Array argument will be: { 11,10,9,8,7,6,5,4,3,2,1 };
long[] arrLargeSides = CurveOrder(nums).ToArray();
Produces: 11 9 7 5 3 1 2 4 6 8 10
Significant namespaces are:
using System;
using System.Collections.Generic;
using System.Linq;
Note: The iterator leaves the decision up to the caller about whether or not to use intermediate storage. The caller might simply be issuing a foreach loop over the results instead.
Extension Method Option
Optionally change the static method header to use the this modifier public static IEnumerable<long> CurveOrder(this long[] nums) { and put it inside a static class in your namespace;
Then call the order method directly on any long[ ] array instance like so:
Array.Reverse(nums); //reverse sort
// Array argument will be: { 11,10,9,8,7,6,5,4,3,2,1 };
long[] arrLargeSides = nums.CurveOrder().ToArray();
Just some (unneeded) syntactic sugar to mix things up a bit for fun. This can be applied to any answers to your question that take an array argument.
I might go for something like this
static T[] SortFromMiddleOut<T, U>(IList<T> list, Func<T, U> orderSelector, bool largestInside) where U : IComparable<U>
{
T[] sortedArray = new T[list.Count];
bool add = false;
int index = (list.Count / 2);
int iterations = 0;
IOrderedEnumerable<T> orderedList;
if (largestInside)
orderedList = list.OrderByDescending(orderSelector);
else
orderedList = list.OrderBy(orderSelector);
foreach (T item in orderedList)
{
sortedArray[index] = item;
if (add)
index += ++iterations;
else
index -= ++iterations;
add = !add;
}
return sortedArray;
}
Sample invocations:
int[] array = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int[] sortedArray = SortFromMiddleOut(array, i => i, false);
foreach (int item in sortedArray)
Console.Write("{0} ", item);
Console.Write("\n");
sortedArray = SortFromMiddleOut(array, i => i, true);
foreach (int item in sortedArray)
Console.Write("{0} ", item);
With it being generic, it could be a list of Foo and the order selector could be f => f.Name or whatever you want to throw at it.
The fastest (but not the clearest) solution is probably to simply calculate the new index for each element:
Array.Sort(array);
int length = array.Length;
int middle = length / 2;
int[] result2 = new int[length];
for (int i = 0; i < array.Length; i++)
{
result2[middle + (1 - 2 * (i % 2)) * ((i + 1) / 2)] = array[i];
}
Something like this?
public IEnumerable<int> SortToMiddle(IEnumerable<int> input)
{
var sorted = new List<int>(input);
sorted.Sort();
var firstHalf = new List<int>();
var secondHalf = new List<int>();
var sendToFirst = true;
foreach (var current in sorted)
{
if (sendToFirst)
{
firstHalf.Add(current);
}
else
{
secondHalf.Add(current);
}
sendToFirst = !sendToFirst;
}
//to get the highest values on the outside just reverse
//the first list instead of the second
secondHalf.Reverse();
return firstHalf.Concat(secondHalf);
}
For your specific (general) case (assuming unique keys):
public static IEnumerable<T> SortToMiddle<T, TU>(IEnumerable<T> input, Func<T, TU> getSortKey)
{
var sorted = new List<TU>(input.Select(getSortKey));
sorted.Sort();
var firstHalf = new List<TU>();
var secondHalf = new List<TU>();
var sendToFirst = true;
foreach (var current in sorted)
{
if (sendToFirst)
{
firstHalf.Add(current);
}
else
{
secondHalf.Add(current);
}
sendToFirst = !sendToFirst;
}
//to get the highest values on the outside just reverse
//the first list instead of the second
secondHalf.Reverse();
sorted = new List<TU>(firstHalf.Concat(secondHalf));
//This assumes the sort keys are unique - if not, the implementation
//needs to use a SortedList<TU, T>
return sorted.Select(s => input.First(t => s.Equals(getSortKey(t))));
}
And assuming non-unique keys:
public static IEnumerable<T> SortToMiddle<T, TU>(IEnumerable<T> input, Func<T, TU> getSortKey)
{
var sendToFirst = true;
var sorted = new SortedList<TU, T>(input.ToDictionary(getSortKey, t => t));
var firstHalf = new SortedList<TU, T>();
var secondHalf = new SortedList<TU, T>();
foreach (var current in sorted)
{
if (sendToFirst)
{
firstHalf.Add(current.Key, current.Value);
}
else
{
secondHalf.Add(current.Key, current.Value);
}
sendToFirst = !sendToFirst;
}
//to get the highest values on the outside just reverse
//the first list instead of the second
secondHalf.Reverse();
return(firstHalf.Concat(secondHalf)).Select(kvp => kvp.Value);
}
Simplest solution - order the list descending, create two new lists, into the first place every odd-indexed item, into the other every even indexed item. Reverse the first list then append the second to the first.
Okay, I'm not going to question your sanity here since I'm sure you wouldn't be asking the question if there weren't a good reason :-)
Here's how I'd approach it. Create a sorted list, then simply create another list by processing the keys in order, alternately inserting before and appending, something like:
sortedlist = list.sort (descending)
biginmiddle = new list()
state = append
foreach item in sortedlist:
if state == append:
biginmiddle.append (item)
state = prepend
else:
biginmiddle.insert (0, item)
state = append
This will give you a list where the big items are in the middle. Other items will fan out from the middle (in alternating directions) as needed:
1, 3, 5, 7, 9, 10, 8, 6, 4, 2
To get a list where the larger elements are at the ends, just replace the initial sort with an ascending one.
The sorted and final lists can just be pointers to the actual items (since you state they're not simple integers) - this will minimise both extra storage requirements and copying.
Maybe its not the best solution, but here's a nifty way...
Let Product[] parr be your array.
Disclaimer It's java, my C# is rusty.
Untested code, but you get the idea.
int plen = parr.length
int [] indices = new int[plen];
for(int i = 0; i < (plen/2); i ++)
indices[i] = 2*i + 1; // Line1
for(int i = (plen/2); i < plen; i++)
indices[i] = 2*(plen-i); // Line2
for(int i = 0; i < plen; i++)
{
if(i != indices[i])
swap(parr[i], parr[indices[i]]);
}
The second case, Something like this?
int plen = parr.length
int [] indices = new int[plen];
for(int i = 0; i <= (plen/2); i ++)
indices[i] = (plen^1) - 2*i;
for(int i = 0; i < (plen/2); i++)
indices[i+(plen/2)+1] = 2*i + 1;
for(int i = 0; i < plen; i++)
{
if(i != indices[i])
swap(parr[i], parr[indices[i]]);
}
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);