C# insert elements in a specific place

[MisterWhite]

Having trouble completing this exercise : Insert a new record (in a specified position, moving the following ones to the right)

so if we have an array of {1,2,3,4,5} , and user wants to add a number ( lets say 7) to a second position (in the 3's position) it would look like {1,2,7,3,4,5}

can someone write the algorithm in c++ or c#

[Nineshadow]

Do you have resizable arrays in C# ? I can't remember, I've been using only C++ for quite some time now. (in C++ we have std::vector)

 

Anyway , the pseudocode should be something like this (considering we don't have resizable arrays)

//read length of arrayread length//declare array with a size bigger than its length, let's say length+1,  to allow for more itemsarray[length+1]//read array...//read value and position of the number to be inserted (let's call the variables value and position)read value , position//shift all values right of the position to the right like so :temp = length + 1while temp > position      array[temp] = array[temp-1]      temp--array[position] = valuelength++                   

[MisterWhite]

Do you have resizable arrays in C# ? I can't remember, I've been using only C++ for quite some time now. (in C++ we have std::vector)

not sure, but the adding method should look similar to deleting an element delete=delete[i+1], but somehow different

[ICantThinkOfAnyGoodName]

There`s already a function for this: https://msdn.microsoft.com/en-us/library/vstudio/bb383995%28v=vs.100%29.aspx

[madknight3]

Do you have resizable arrays in C# ?

 

Yeah, it's List<> in C#. Probably best for the OP to learn how to do it manually first though (which I see you've edited in now).

[MisterWhite]

There`s already a function for this: https://msdn.microsoft.com/en-us/library/vstudio/bb383995%28v=vs.100%29.aspx

will this work in c#?

[Shoob]

Do you have resizable arrays in C# ? I can't remember, I've been using only C++ for quite some time now. (in C++ we have std::vector)

I think no. He will have to use a list.

 

There`s already a function for this: https://msdn.microsoft.com/en-us/library/vstudio/bb383995%28v=vs.100%29.aspx

I think that's only for JavaScript. He'll have to use Insert or Add method for a list.

[ICantThinkOfAnyGoodName]

I think no. He will have to use a list.

 

I think that's only for JavaScript. He'll have to use Insert or Add method for a list.

Didn`t notice that. I thought C# also had a function like that. Although arrays are resizable in C#(this time a link that is actually about C# and not JS). https://msdn.microsoft.com/en-us/library/bb348051%28v=vs.110%29.aspx

[Shoob]

Didn`t notice that. I thought C# also had a function like that. Although arrays are resizable in C#(this time a link that is actuallt about C# and not JS). https://msdn.microsoft.com/en-us/library/bb348051%28v=vs.110%29.aspx

Oh nice, I didn't knew that method - I'll try it. But still, lists are awesome. 

[MisterWhite]

I think no. He will have to use a list.

 

I think that's only for JavaScript. He'll have to use Insert or Add method for a list.

if i have an array that has some strings in it, can i make array=list (pseudo code)

[madknight3]

Didn`t notice that. I thought C# also had a function like that. Although arrays are resizable in C#(this time a link that is actually about C# and not JS). https://msdn.microsoft.com/en-us/library/bb348051%28v=vs.110%29.aspx

 

Oh nice, I didn't knew that method - I'll try it. But still, lists are awesome. 

 

Arrays are not resizable in C#. That method creates a new array with the new size and copies over the data from the old array.

 

List, which is a C# implementation of the dynamic array data structure, does this for you behind the scenes as you add items to it.

[Nineshadow]

Arrays are not resizable in C#. That method creates a new array with the new size and copies over the data from the old array.

 

List, which is a C# implementation of the dynamic array data structure, does this for you behind the scenes as you add items to it.

Lists in C# aren't linked lists?

[Shoob]

if i have an array that has some strings in it, can i make array=list (pseudo code)

List<string> someList = new List<string>(someArray);

[ICantThinkOfAnyGoodName]

Arrays are not resizable in C#. That method creates a new array with the new size and copies over the data from the old array.

 

List, which is a C# implementation of the dynamic array data structure, does this for you behind the scenes as you add items to it.

I know, but it still works the same as if you had a resizable array in C# most of the time.

[madknight3]

Lists in C# aren't linked lists?

 

C# has a separate class called LinkedList for that (it was mentioned in the link in my reply to you above).

[MisterWhite]

List<string> someList = new List<string>(someArray);

after this ill be allowed to do anything with my old arrays elements but with list functions?

[Shoob]

after this ill be allowed to do anything with my old arrays elements but with list functions?

No, that way you make a list, which contains the elements of the array.

[MisterWhite]

No, that way you make a list, which contains the elements of the array.

maybe my question was incorrect, but i meant what you answered

[madknight3]

maybe my question was incorrect, but i meant what you answered

 

Using a List is defeating the purpose of the exercise which is teaching you how to work with arrays.

 

But hey, you're still learning. You're just learning how to use a List instead which is a very useful class to know how to use. I'd recommend learning how to do the exercise both ways.

[MisterWhite]

Using a List is defeating the purpose of the exercise which is teaching you how to work with arrays.

 

But hey, you're still learning. You're just learning how to use a List instead which is a very useful class to know how to use. I'd recommend learning how to do the exercise both ways.

i just didn't receive any help on doing it with arrays

[Shoob]

i just didn't receive any help on doing it with arrays

Check Nineshadow's pseudocode - it can give you a general understanding and you can build the program around it.  

 

The list way is much simpler, but your teacher won't be happy with it.

Example:

int[] arr = {1,2,3,4,5};List <int> list = new List<int>(arr);list.Insert(2, 7); //insert "7" at the second positionforeach (var item in list){    Console.Write(item + " ");}

[Nineshadow]

The following is made in C++. Don't know how it should work in C#.

 

This is an insert function :

void insert(int **v, int length, int pos, int value){    int *t = new int[length+1];    int *q = *v;    for(int i = 0; i < pos; i++)        *(t+i) = q[i];    *(t+pos) = value;    for(int i = pos; i < length; i++)        *(t+i+1) = q[i];    *v = t;}

Its input is represented of : a pointer to the pointer of the array (since we will be editing the array's pointer) , the length of the array, value and position of the number to be inserted.

We create a new array of size length+1 at a pointer, let's call it T.

Then, we create a new int pointer which points to the original array, let's call it Q.

We copy everything from [0,pos-1] of Q into our new array T at a corresponding location ( T = Q)

We copy value into T[pos].

Then, we copy all elements from [pos,length] from Q into T at [pos+1,length+1] ( T[i+1] = Q )

Next, we put T  (a pointer to the final array) into the value pointed by the first pointer of the double pointer.

 

This basically overwrites our original array with the new T array.

 

However, in order to use this function you need to use a dynamically allocated array.

An example of using this function :

#include <iostream>using namespace std;void insert(int **v, int length, int pos, int value){    int *t = new int[length+1];    int *q = *v;    for(int i = 0; i < pos; i++)        *(t+i) = q[i];    *(t+pos) = value;    for(int i = pos; i < length; i++)        *(t+i+1) = q[i];    *v = t;}int main(){    int *v = new int[4];    v[0]=1;    v[1]=2;    v[2]=4;    v[3]=5;    insert(&v, 4, 2, 3);    for( int i = 0; i < 5; i++)        cout << v[i] << ' ';    return 0;}

We create a new dinamically allocated array : [1,2,4,5].

We call the insert function to put 3 into the position 2 of the array.

When we write our array, we end up with : [1,2,3,4,5].

 

It's different than the method I mentioned with pseudocode.

That one would work like this :

#include <iostream>#include <fstream>using namespace std;ifstream in("test.in");#define MAX 1000int main(){    int length;    in >> length;    int v[MAX];    for(int i = 0; i < length;i++) in >> v[i];    int position, value;    in >> position >> value;    for(int temp = length+1; temp > position; temp--)    {        v[temp] = v[temp-1];    }    v[position] = value;    length++;    for(int i = 0; i < length; i++) cout << v[i];    return 0;}

For this input file :

41 2 4 52 3

It writes :

1 2 3 4 5

Just as it should.

It probably should work in C# as well, with a little changes.

[ICantThinkOfAnyGoodName]

i just didn't receive any help on doing it with arrays

Can`t test this code right now because my visual studio license is expired and I`m to lazy to download VS express, but here`s what I`d do if it has to be as an array:

int[] a = {1, 2, 3, 4, 5};int insertObjectAtIndex = 2;int insertValue = 100;int[] b = new int[a.Length+1];for (int i=0;i<=a.Length;i++) {  if(i==insertObjectAtIndex){    b[i]=insertValue;    i++;  }  b[i]=a[i];} return b;

Obviously this isn`t a complete function, but you should get the idea.

[Nineshadow]

Can`t test this code right now because my visual studio license is expired and I`m to lazy to download VS express, but here`s what I`d do if it has to be as an array:

int[] a = {1, 2, 3, 4, 5};int insertObjectAtIndex = 2;int insertValue = 100;int[] b = new int[a.Length+1];for (int i=0;i<=a.Length;i++) {  if(i==insertObjectAtIndex){    b[i]=insertValue;    i++;  }  b[i]=a[i];} return b;

The problem with your code is that it doesn't make a correct correlation between the two arrays after the new element is inserted.

Let's take your own example.

Once i reaches 2, b = 100, so b[2]=100, then i gets incremented and b = a, so b[3] = a[3] = 4

We obviously missed a[2].

[ICantThinkOfAnyGoodName]

 

Check Nineshadow's pseudocode - it can give you a general understanding and you can build the program around it.

 

The list way is much simpler, but your teacher won't be happy with it.

Example:

int[] arr = {1,2,3,4,5};List <int> list = new List<int>(arr);list.Insert(2, 7); //insert "7" at the second positionforeach (var item in list){    Console.Write(item + " ");}

I hate it when teachers tell me that my solution is bad. Today I had to do this exersize in school: http://codingbat.com/prob/p130788

This was my solution:

public int luckySum(int a, int b, int c) {  return a==13?0:(b==13?a:(c==13?a+b:a+b+c));}

But he told me that it was badly readable and I should do it with "if" instructions, which would have taken up at least 5 times more space.