I am a rookie to C# and here is my question
class myClass
{
int start;
int end;
.......
}
class program
{
public void main()
{
myClass[] a= new myClass[10];
for (int i = 1; i < a.length; i++)
{
myClass b = new myClass();
a[i] = b;
a[i].start = 1;
... (keep populating)
...
}
console.writeline(a[1].start) // NO PROBLEM WITH THIS LINE, THE VALUE WAS OUTPUTED
subMethod(a);
}
public void subMethod(myClass[] a)
{
console.write(a[1].start); // NO PROBLEM WITH THIS LINE, OUTPUT NORMALLY
for (int i = 1; i < a.length, i++)
{
int h = a[i].start; ????? OBJECT NOT INSTANTIATED
}
}
}
The error is as indicated above and I have difficulty to understand it. Anyone can help me out. Thanks in advance
The problem seems to be in the code that you haven't posted.
myClass[] a= new myClass[10];
// (populate this array)
I've no idea what you have written there but it clearly isn't working. It should be this:
myClass[] a = new myClass[10];
for (int i = 0; i < a.Length; i++)
{
a[i] = new myClass();
}
The code you posted won't compile. Please copy + paste the actual code - don't try to write it from memory.
You should notice that the first index in an array is 0, not 1.
I'd also suggest that you read the Microsoft naming guidelines, for example class names should be in Pascal case.
You've instantiated an array but new need to instantiate each object in the array. You are not showing how you do that bit in the example above.
Please post code that compiles. The error is probably in your transcribing of the code, because this code works perfectly fine:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace RandomArrayTest
{
class MyClass
{
public int start;
}
class Program
{
static void Main(string[] args)
{
MyClass[] a = new MyClass[10];
for(int i=1; i<a.Length; i++)
{
MyClass b = new MyClass();
a[i] = b;
a[i].start = 1;
}
MyFunction(a);
}
static void MyFunction(MyClass[] a)
{
for (int i = 1; i < a.Length; i++)
{
int h = a[i].start;
Console.WriteLine(h);
}
}
}
}
Related
i have this:
private static List<Mod> m_modList;
public static void UpdateScript(Script rScript)
{
for (int i = 0; i < m_modList.Count; i++)
for (int b = 0; b < m_modList[i].scriptModule.Count; b++)
for (int m = 0; m < m_modList[i].scriptModule[b].scripts.Count; m++)
if (m_modList[i].scriptModule[b].scripts[m].name == rScript.name)
m_modList[i].scriptModule[b].scripts[m] = rScript;
}
can I somehow reduce the amount of code, and not use so many for loops?
First, you could simplify your code for better understanding (even for yourself) :
foreach(Mod mod in m_modList)
{
foreach(ScriptMod scriptMod in mod.scriptModule)
{
for(int i = 0;i<scriptMod.scripts.Count();i++)
{
if(scriptModule.scripts[i].name==rScript.name)
scriptModule.scripts[i]=rScript;
}
}
}
You eventually could simplify it like that :
foreach(ScriptModule scriptMod in m_modList.SelectMany(x=>x.scriptModule))
{
for(int i = 0;i<scriptModule.scripts.Count();i++)
{
if(scriptModule.scripts[i].name==rScript.name)
scriptModule.scripts[i]=rScript;
}
}
in the case scriptModule.scripts[i]=rScript; could be replaced by a Clone, you can use several SelectMany :
foreach(Script script in m_modList.SelectMany(x=>x.scriptModule.SelectMany(y=>y.scripts)))
{
if(script.Name==rScript.Name)
{
script.Clone(rScript);
}
}
(cannot assign an object in foreach).
I am learning C# and want to created a weighted job scheduler.
The max profit is working fine. But I need to be able to get the JobIDs associated with it so I am trying to save it in an array jobsId, similar to this implementation in C++: https://onlinegdb.com/a9wx3nHoN.
But then in this snippet, I am getting an error: Wrong number of indices inside []; expected 2
if (profitSum > dp[i-1]) {
dp[i] = profitSum;
jobsId[i,0] = jobsId[task]; // Problem is here
jobsId[i].Append(jobs[i].id).ToArray(); //And here
}
What am I doing wrong? Please help, thanks!
Codes can be accessed here:
https://rextester.com/NXM85235
Alternatively, here is my entire snippet:
using System.IO;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.Linq;
class Program
{
public int JobScheduling(int[] startTime, int[] endTime, int[] profit) {
var jobs = startTime
.Select((_, i) => new // create custom obj
{
id = i,
s = startTime[i],
e = endTime[i],
p = profit[i],
}
)
.OrderBy(x => x.e) // sort by end-time
.ToArray();
int[] dp = new int[jobs.Length];
int [,] jobsId = new int[,] {{jobs[0].id}};
int profitSum = jobs[0].p;
int task = -1;
dp[0] = jobs[0].p;
for (var i = 1; i < jobs.Length; i++) {
for (var j = i-1; j >= 0; j--) {
if (jobs[j].e <= jobs[i].s) {
task = j;
break;
}
}
if (task != -1) {
profitSum += dp[task];
}
if (profitSum > dp[i-1]) {
dp[i] = profitSum;
jobsId[i,0] = jobsId[task]; // Problem is here
jobsId[i].Append(jobs[i].id).ToArray();
}
}
// Need to implement this
for (var iter = 0; iter < jobsId.Length; iter++) {
Console.WriteLine(jobsId[iter,0]);
}
return dp[jobs.Length-1];
}
public static void Main(string[] args)
{
int[] startTime = { 1,3,6,2 };
int[] endTime = { 2,5,7,8 };
int[] profit = { 50,20,100,200 };
// Creating object
Program job = new Program();
Console.WriteLine(job.JobScheduling(startTime, endTime, profit));
}
}
int [,] jobsId = new int[,] {{jobs[0].id}};
The multi-dimensional 3d array that you are using has a fixed size .i.e. only one. You can't add any more elements to that array. Instead, try using List< List < int > >.
jobsId[i,0] = jobsId[task]; // problem here
Here jobsId is a 2d-array. You can't access the individual rows. You can only access elements within. For this too you need to create an array of array .i.e List< List < int > >.
And I could not figure out why are trying to get an array here.
jobsId[i].Append(jobs[i].id).ToArray();
I am having an issue with picking randomly from a list. When I run the program, it keeps writing the same string over and over again when I want it to come up with a different random string each time. Here is an example:
using System;
using System.Collections.Generic;
namespace List
{
class Program
{
static void Main(string[] args)
{
var letterList = new List<string>
{
"A","B","C","D"
};
Random r = new Random();
int letterListIndex = r.Next(letterList.Count);
for (int i = 0; i < 10; i++) {
Console.WriteLine(letterList[letterListIndex]);
}
}
}
}
For Example: When I run this code it would write "B" 10 times. I want it to come up with 10 different letters every time. I know that you could just write:
int letterListIndex1 = r.Next(letterList.Count);
int letterListIndex2 = r.Next(letterList.Count);
int letterListIndex3 = r.Next(letterList.Count);
Console.WriteLine(letterList[letterListIndex1]);
Console.WriteLine(letterList[letterListIndex2]);
Console.WriteLine(letterList[letterListIndex3]);
But I wanted to know if there was an easier way to do so.
Thanks.
You should put your letterListIndex variable inside for loop
for (int i = 0; i < 10; i++) {
int letterListIndex = r.Next(letterList.Count);
Console.WriteLine(letterList[letterListIndex]);
}
Otherwise you get the same index every time.
You need to put
int letterListIndex = r.Next(letterList.Count);
inside the for loop.
you can use below code
for (int i = 0; i < 10; i++) {
Console.WriteLine(letterList[r.Next(letterList.Count)]);
}
Cbooks has an atribute "CTeam[] Teams" and it is of fixed size (8). If I want to add objects to it using this in the Main:
CBook A1 = new CBook("Title1", "Author1");
CBook A2 = new CBook("Title1", "Author2");
CBooks ArrayOfBooks = new CBooks(8);
ArrayOfBooks.Add(A1);
ArrayOfBooks.Add(A2);
then position 0 and 1 are ocuppied, and the positions from 2 to 7 are null. What I want to do is, using a variable "int aux=0", count the ocupied positions like this:
for (int k = 0; k < NumberOfTeams; k++)
{
if (Teams[k].Name=="")
Aux += 1;
}
So, Aux in this case would be 2, then I want to do "Teams[Aux] = A" so that A would be in the position 2 and now I should have three objects in my array. But I'm getting "Index out of bound"
Your implementation then should look similar to this:
public class Program
{
public static void Main(string[] args)
{
Element a = new Element("A");
Element b = new Element("B");
MyArray array = new MyArray(8);
array.Add(a);
array.Add(b);
Console.WriteLine(array.Count()); //2 Elements are in the array
}
}
//Sample element class.
public class Element{
public readonly String MyString;
public Element(String myString){
MyString = myString;
}
}
//Sample array class.
public class MyArray{
private readonly Element[] myArray;
private int count; //Use a property here
public MyArray(int size){
//Be careful -> check if size is >= 0.
myArray = new Element[size];
}
public bool Add(Element element){
if(myArray.Length == count) // return false if no more elements fit.
return false;
myArray[count] = element;
count++;
return true;
}
public int Count(){
return count;
}
}
So there is no need for creating an extra count loop. Your "count" variable in "MyArray" class holds always the correct value.
Anyway the implementation or use case of this code is a little bit clunky.
Why are you cant use directly a more safe list or something. That would be a better solution.
What do you need CBooks for? From what I understand, it's just an array of 8 CBook objects so why not use CBook[]?
CBook A1 = new CBook("Title1", "Author1");
CBook A2 = new CBook("Title1", "Author2");
CBooks[] ArrayOfBooks = new CBook[8];
ArrayOfBooks[0] = A1;
ArrayOfBooks[1] = A2;
int aux = 0;
for (int k = 0; k < ArrayOfBooks.Length; k++)
{
//break the loop because we know there are no more books
if (ArrayOfBooks[k] == null)
break;
aux++;
}
The question doesn't cover what the variables NumberOfTeams and Teams are for but could those be added to the implementation of CBook?
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication18
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Sisesta suvaline tekst-->");
string tekst1 = Console.ReadLine();
// string tekst2 = ("ja");
char jtaht = ('j');
char ataht = ('a');
int jsidOntekstis = 0;
int asidOnTekstis = 0;
int tekstipikkus = tekst1.Length;
int jasidonTekstis = jsidOntekstis + asidOnTekstis;
int jasidEiOleTekstis=1;
for (int i = 0; i < tekstipikkus; i++)
{
if (tekst1[i] == jtaht)
{
jsidOntekstis++;
}
if (tekst1[i] == ataht)
{
asidOnTekstis++;
}
}
// for (int k = 0; i < tekstipikkus; i++)
{
{
if (jasidonTekstis > jasidEiOleTekstis)
{
Console.Write("Ja on tekstis olemas");
}
else
{
Console.Write("Ja-sid ei ole tekstis");
}
}
}
Console.ReadKey();
}
}
}
So This is my code and it isn't working the way it should. My teacher asked me to search for "ja" in text without contain method so we would think more logically. I completed all other exercises but this one. Thank you!
StackOverflow is actually not a place where people DO something for you.
They help you and tell you HOW to do this. This issue contains only the wrong piece of code and question "what's wrong".
First of all, I need to tell you that the first problem is, obviously, the algorithm.
I can't understand what is your code supposed to do because even you don't understand it.
using System;
using System.Text;
namespace ConsoleApplication18
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Where to search -->");
string text = Console.ReadLine();
string pattern = "ja"; // Probably, it is better to get it from Console as well
for (int i = 0; i < text.Length; i++)
{
for (int j = 0; j < pattern.Length; j++)
{
if (text[i+j] == pattern[j] && j == pattern.Length - 1)
Console.WriteLine(i);
if (text[i+j] != pattern[j]) break;
}
}
}
}
}
Here is the (not a best) code which searches for the pattern in the text without Contains method. It iterates through the text string - and if it meets the first character of pattern string - it goes further comparing characters one by one in a row. If the inner loop iterated till the end then it means that text string contains pattern string and outputs it's position. If in any moment characters are not equal then the inner loop breaks and continues the main loop.
Research it and understand it. Then you can solve the problem.