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Domino recursion

I have a recursion assignment where I have to input into console the following data:
On the first line a natural number equal with the number of tiles I have to input on the following lines (in my example the first number is 6).
On the following lines the domino tiles in the following order:
1 2
1 3
3 4
2 3
3 5
4 5
On the last line another number representing the number of tiles that needs to be returned on each separate line (in my example the number is equal with 3).
With this data I have to display all possible combinations of pairs. For each separate line the number the second number from the first pair has to be equal with the first number of the following pair and so on. I had a hint for this assignment where I have to declare an intermediary list that is equal with the function (using recursion from the start) but when I'm trying to run the code it gives me a null exception for the intermediaryList.
In the first instance I read the data as a 2d array but settled with a simple string array where.
This is my code so far, could you help me with a suggestion, how to avoid the null exception?
(sorry if I missed something from the explanation, this is my second post here so far and thank you in advance). Also I have to mention that I'm allowed to use just "using System;" Not allowed to use Linq or anything else.
enter code here
static string[] ReadDominoTiles(int n)
{
string[] input = new string[n];
for (int i = 0; i < n; i++)
{
input[i] = Console.ReadLine();
}
return input;
}
static string[] DominoSolution(string[] dominoTiles, int numberOfPairs)
{
string[] finalList = new string[numberOfPairs];
if (numberOfPairs == 1)
{
return finalList;
}
string[] intermediaryList = DominoSolution(dominoTiles, numberOfPairs - 1);
for (int i = 0; i < intermediaryList.Length; i++)
{
for (int j = 0; j < dominoTiles.Length; j++)
{
// This is where I get the nullref exception, every value from intermediaryList is null
if (intermediaryList[i] != dominoTiles[j] && intermediaryList[j][1] == dominoTiles[j][0])
{
finalList[j] += intermediaryList[j] + " " + dominoTiles[j];
}
}
}
return finalList;
}
static void Main(string[] args)
{
int n = Convert.ToInt32(Console.ReadLine());
string[] dominoTiles = ReadDominoTiles(n);
int numberOfPairs = Convert.ToInt32(Console.ReadLine());
Console.WriteLine(DominoSolution(dominoTiles, numberOfPairs));
}

This is where I get the nullref exception, every value from intermediaryList is null
That's correct, you call the function recursively after doing exactly zero work, besides adding a recursion termination condition which returns an array of nulls. So the first time you come out of your recursion you have in intermediaryList a number of null elements, so when you pretend they're strings and try to get intermediaryList[j][1] you'll get a null reference exception.
As to the solution, it's not exactly clear what's with all the arrays you're allocating. Use a List<> with an actual type and do your work properly. Though I hate to break it to you but if I understand your assignment correctly the solution will use backtracking and combinatorics, which is much more code and much better structured than what you have here.

Generating a variable number of random numbers to a list, then comparing those numbers to a target?

How would I go about generating a serializable variable of random numbers to a list, then comparing those generated numbers to a target number?
What I want to do is make a program that takes in a number, such as 42, and generates that number of random numbers to a list while still keeping the original variable, in this case 42, to be referenced later. Super ham-handed pseudo-code(?) example:
public class Generate {
[SerializeField]
int generate = 42;
List<int> results = new List<int>;
public void Example() {
int useGenerate = generate;
//Incoming pseudo-code (rather, code that I don't know how to do, exactly)
while (useGenerate => 1) {
results.add (random.range(0,100)); //Does this make a number between 0 and 99?
int useGenerate = useGenerate - 1;
}
}
}
I think this will do something to that effect, once I figure out how to actually code it properly (Still learning).
From there, I'd like to compare the list of results to a target number, to see how many of them pass a certain threshold, in this case greater than or equal to 50. I assume this would require a "foreach" thingamabobber, but I'm not sure how to go about doing that, really. With each "success", I'd like to increment a variable to be returned at a later point. I guess something like this:
int success = 50;
int target = 0;
foreach int in List<results> {
if (int => success) {
int target = target + 1;
}
}
If I have the right idea, please just teach me how to properly code it. If you have any suggestions on how to improve it (like the whole ++ and -- thing I see here and there but don't know how to use), please teach me that, too. I looked around the web for using foreach with lists and it seemed really complicated and people were seemingly pulling some new bit of information from the Aether to include in the operation. Thanks for reading, and thanks in advance for any advice!

Unity formatting multiple numbers

So I'm a complete newb to unity and c# and I'm trying to make my first mobile incremental game. I know how to format a variable from (e.g.) 1000 >>> 1k however I have several variables that can go up to decillion+ so I imagine having to check every variable's value seperately up to decillion+ will be quite inefficient. Being a newb I'm not sure how to go about it, maybe a for loop or something?
EDIT: I'm checking if x is greater than a certain value. For example if it's greater than 1,000, display 1k. If it's greater than 1,000,000, display 1m...etc etc
This is my current code for checking if x is greater than 1000 however I don't think copy pasting this against other values would be very efficient;
if (totalCash > 1000)
{
totalCashk = totalCash / 1000;
totalCashTxt.text = "$" + totalCashk.ToString("F1") + "k";
}

So, I agree that copying code is not efficient. That's why people invented functions!
How about simply wrapping your formatting into function, eg. named prettyCurrency?
So you can simply write:
totalCashTxt.text = prettyCurrency(totalCashk);
Also, instead of writing ton of ifs you can handle this case with logarithm with base of 10 to determine number of digits. Example in pure C# below:
using System.IO;
using System;
class Program
{
// Very simple example, gonna throw exception for numbers bigger than 10^12
static readonly string[] suffixes = {"", "k", "M", "G"};
static string prettyCurrency(long cash, string prefix="$")
{
int k;
if(cash == 0)
k = 0; // log10 of 0 is not valid
else
k = (int)(Math.Log10(cash) / 3); // get number of digits and divide by 3
var dividor = Math.Pow(10,k*3); // actual number we print
var text = prefix + (cash/dividor).ToString("F1") + suffixes[k];
return text;
}
static void Main()
{
Console.WriteLine(prettyCurrency(0));
Console.WriteLine(prettyCurrency(333));
Console.WriteLine(prettyCurrency(3145));
Console.WriteLine(prettyCurrency(314512455));
Console.WriteLine(prettyCurrency(31451242545));
}
}
OUTPUT:
$0.0
$333.0
$3.1k
$314.5M
$31.5G
Also, you might think about introducing a new type, which implements this function as its ToString() overload.
EDIT:
I forgot about 0 in input, now it is fixed. And indeed, as #Draco18s said in his comment nor int nor long will handle really big numbers, so you can either use external library like BigInteger or switch to double which will lose his precision when numbers becomes bigger and bigger. (e.g. 1000000000000000.0 + 1 might be equal to 1000000000000000.0). If you choose the latter you should change my function to handle numbers in range (0.0,1.0), for which log10 is negative.

How to cycle through an (n by 12) 2D array

I have a 2-D array (with dimensions magnitudes n by 5), which I'm picturing in my head like this (each box is an element of the array):
(http://tr1.cbsistatic.com/hub/i/2015/05/07/b1ff8c33-f492-11e4-940f-14feb5cc3d2a/12039.jpg)
In this image, n is 3. I.e, n is the number of columns, 5 is the number of rows in my array.
I want to find an efficient way to iterate (i.e walk) through every path that leads from any cell in the left most column, to any cell in right most column, choosing one cell from every column in between.
It cannot be simply solved by n nested loops, because n is only determined at run time.
I think this means recursion is likely the best way forward, but can't picture how to begin theoretically.
Can you offer some advice as to how to cycle through every path. It seems simple enough and I can't tell what I'm doing wrong. Even just a theoretical explanation without any code will be very much appreciated.
I'm coding in C#, Visual Studio in case that helps.
UPDATE:: resolved using code below from http://www.introprogramming.info/english-intro-csharp-book/read-online/chapter-10-recursion/#_Toc362296468
static void NestedLoops(int currentLoop)
{
if (currentLoop == numberOfLoops)
{
return;
}
for (int counter=1; counter<=numberOfIterations; counter++)
{
loops[currentLoop] = counter;
NestedLoops(currentLoop + 1);
}
}

This is a factorial problem and so you might run quite quickly into memory or value limits issues.
Took some code from this SO post by Diego.
class Program
{
static void Main(string[] args)
{
int n = 5;
int r = 5;
var combinations = Math.Pow(r, n);
var list = new List<string>();
for (Int64 i = 1; i < combinations; i++)
{
var s = LongToBase(i);
var fill = n - s.Length;
list.Add(new String('0', fill) + s);
}
// list contains all your paths now
Console.ReadKey();
}
private static readonly char[] BaseChars = "01234".ToCharArray();
public static string LongToBase(long value)
{
long targetBase = BaseChars.Length;
char[] buffer = new char[Math.Max((int)Math.Ceiling(Math.Log(value + 1, targetBase)), 1)];
var i = (long)buffer.Length;
do
{
buffer[--i] = BaseChars[value % targetBase];
value = value / targetBase;
}
while (value > 0);
return new string(buffer);
}
}
list will contain a list of numbers expressed in base 5 which can be used to found out the path. for example "00123" means first cell, then first cell then second cell, then third cell and finall fourth cell.

Resolved:: see the code posted in the edited question above, and the link to a recursion tutorial, where it takes you through using recursion to simulate N nested, iterative loops.

passing a result(double type variable) from a method as an element of an array

Background -
I am new to programming in C# and am trying to code a custom indicator. On a trading platform that uses C#. A histogram with
positive Y axis = reqAskArraySum
negative Y axis = reqBidArraySum
The inbuilt compiler shows no errors. However the desired results do not seem to show up.
I know/it is possible there are some platform specific initialization problems i.e. code that I have not entered yet correctly.
Question -
The question here is with regards to the code posted below , which is a part of the whole code.
I would like to know whether the posted code satisfies the below objectives.
The objective here is to get a 'number' using a method.
Then only accept selected 'numbers' into an array. The selection/filtration is done by an 'If' statement
Any help and pointers would be highly appreciated.
int i=0;
double iAskSize = GetLevel2Size(ASK,0); //GetLevel2Size(ASK,0) is the method that helps me to retrieve the ASK side 'numbers'//
double iBidSize = GetLevel2Size(BID,0); //GetLevel2Size(BID,0) is the method that helps me to retrieve the BID side 'numbers' //
if(iAskSize>=AskTH_value) //the number should be >= user defined AskTH_value, this is the filtration of the Ask Side 'numbers'//
I am trying to get the filtered iAskSize 'numbers' into the array
reqAskSize, I believe there is a problem here. However I am not sure
{
double[] reqAskSize = new double[1000];
double reqAskArraySum = 0;
for(i=0;i<reqAskSize.Length;i++)
{
reqAskArraySum = reqAskArraySum + reqAskSize[i];
}
SetValue(0,reqAskArraySum);
}
if(iBidSize>=BidTH_value) **//the number should be >= user defined BidTH_value,this is the filtration of the Bid Side 'numbers'//**
I am trying to get the filtered iBidSize 'numbers' into the array
reqBidSize, I believe there is a problem here. However I am not sure
{
double[] reqBidSize = new double[1000];
double reqBidArraySum = 0;
for(i=0;i<reqBidSize.Length;i++)
{
reqBidArraySum = reqBidArraySum + reqBidSize[i];
}
SetValue(1,-reqBidArraySum);
}

If you are trying to add selected numbers into an array, once a number has been selected (through a conditional like if/else), the number should be set in the array.
For example
int[] array = new int[6];
for(int val = 0; val < 6; val++)
{
if(array[val] > 0)
array[val] = 6;
}
Also to obtain a numeral, a return statement makes clear if anything is got.
You should try and see where a return statement may belong within your code.