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What should I do to get arr2 from arr? [closed]

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I have a array need to handles values that are not null
var arr = [null,2,null,5,4];
var _arr = RemoveNull(arr); // [2,5,4]
var _arr2 = Encrypt(_arr); // [e1,e2,e3]
var arr2 = Tansform(_arr2); //[null,e1,null,e2,e3]
What should I do to get arr2 from arr?

In Encrypt method, you can ignore null. What exactly is the array data type?
public static void Main()
{
int?[] Arr = new int?[] { null,2,null,5,4 };
string[] OutArr = SkipNullAndEncrypt(Arr);
foreach(string Item in OutArr)
{
Console.Write(Item + " ");
}
//Output: null e2 null e5 e4
}
private static string[] SkipNullAndEncrypt(int?[] InArr)
{
int Len = InArr.Length;
string[] OutArr = new string[Len];
int i = 0;
foreach(int? ThisItem in InArr)
{
if(ThisItem.HasValue)
{
//Encrypt call here. I have just concatenated.
OutArr[i] = "e" + ThisItem.Value.ToString();
}
else
{
OutArr[i] = "null"; // Only to make it visible in the output
}
i++;
}
return OutArr;
}
From you comment, this is how you can do it:
using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main()
{
string[] Arr = new string[] { null, "2", null, "5", "4" };
string[] ArrNullRemoved = RemoveNull(Arr);
DisplayArr(ArrNullRemoved); //2 5 4
string[] EncArr = EncryptArr(ArrNullRemoved);
DisplayArr(EncArr);//e2 e5 e4
string[] FinArr = TransformArr(EncArr, Arr);
DisplayArr(FinArr);//null e2 null e5 e4 
}
private static string[] TransformArr(string[] EncArr, string[] OgArr)
{
string[] OutArr = new string[OgArr.Length];
int i = 0;
int E_Pointer = 0;
foreach(string Item in OgArr)
{
if(string.IsNullOrWhiteSpace(Item))
{
OutArr[i] = "null"; //Only for display
}
else
{
OutArr[i] = EncArr[E_Pointer];
E_Pointer++;
}
i++;
}
return OutArr;
}
private static string[] RemoveNull(string[] InArr)
{
return InArr.Where(a => !string.IsNullOrWhiteSpace(a)).ToArray();
}
private static void DisplayArr(string[] InArr)
{
foreach(string Item in InArr)
{
Console.Write(Item + " ");
}
Console.WriteLine();
}
private static string[] EncryptArr(string[] InArr)
{
int i = 0;
foreach(string Item in InArr)
{
InArr[i] = "e" + Item;
i++;
}
return InArr;
}
}

string[] arr = new string[5] { null, "b", "c", null, "e" };
var _arr = RemoveNull(arr );
var _arr2 = Encrypt(_arr);
List<string> temp = new();
int j = 0;
for (int i = 0; i < arr .Length; i++)
{
if (arr [i] == null)
temp.Add(null);
else
{
temp.Add(_arr2 [j]);
j++;
}
}
var arr2 = temp.ToArray();
Input { null, "b", "c", null, "e" }
output
[
null,
"eb",
"ec",
null,
"ee"
]

Putting two 1D arrays into one 2D array in c#

Hey guys i have two 1D arrays one with names and one with phonenumbers:
private string[] names = { "xaw", "Tommy", "Alan", "Sergio", "Adam", "Pablo" };
private string[] phones = { "535-4213", "535-0421", "722-352", "070-3531", "343-2324", "344-2223" };
I want to put them into one 2D array.
also do i have to declare array size like this:
string[,] phonesNames = new string[6,2]
or can i leave it like this:
(without declaration of size? Will it work in this case?)
string[,] phonesNames;
The result should be pairs so phoneNames[0,0] is xaw and phoneNames[0,1] is 535-4213 like this:
Xaw 535-4213
Tommy 535-0421
Alan 722-352
Sergio 070-3531
Adam 343-2324
Pablo 344-2223
I would greatly appreciate if you helped me please.
#edit This is actually not the solution because it only appears as sorted with Console.Writeline() the array is now [2,6] but the thing i was searching for was sorted array [6,2]
private static void Main(string[] args)
{
string[] names = { "xaw", "Tommy", "Alan", "Sergio", "Adam", "Pablo" };
string[] phones = { "535-4213", "535-0421", "722-352", "070-3531", "343-2324", "344-2223" };
string[,] phonesNames = new string[2, names.Length];
for (var i = 0; i < names.Length; i++)
{
phonesNames[0, i] = names[i];
phonesNames[1, i] = phones[i];
}
for (int i = 0; i < names.Length; i++)
Console.WriteLine("{0} {1}", phonesNames[0,i], phonesNames[1,i]);
}
}
The solution is in just 2 lines of code in for loop
for (int dimension = 0; dimension < 6; dimension++)
{
phonesNames[dimension, 0] = names[dimension];
phonesNames[dimension, 1] = phones[dimension];
}

string[] names = { "xaw", "Tommy", "Alan", "Sergio", "Adam", "Pablo" };
string[] phones = { "535-4213", "535-0421", "722-352", "070-3531", "343-2324", "344-2223" };
string[][] phoneNames = new string[2][];
phoneNames[0] = names;
phoneNames[1] = phones;
for (int i = 0; i < names.Length; i++)
Console.WriteLine("{0} {1}", phoneNames[0][i], phoneNames[1][i]);
[![enter image description here][1]][1]

Also, you can use ZIP Method
(https://learn.microsoft.com/en-us/dotnet/api/system.linq.enumerable.zip?view=net-6.0)\
string[] names = { "xaw", "Tommy", "Alan", "Sergio", "Adam", "Pablo" };
string[] phones = { "535-4213", "535-0421", "722-352", "070-3531", "343-2324", "344-2223" };
var zipped = names.Zip(phones, (one, two) => one + " " + two);
foreach(string name in zipped)
{
Console.WriteLine(name);
}
Output
xaw 535-4213
Tommy 535-0421
Alan 722-352
Sergio 070-3531
Adam 343-2324
Pablo 344-2223

If you want to combine the two 1D arrays into one 2D array, this is what I will do:
internal class Program
{
private static readonly string[] names = { "xaw", "Tommy", "Alan", "Sergio", "Adam", "Pablo" };
private static readonly string[] phones = { "535-4213", "535-0421", "722-352", "070-3531", "343-2324", "344-2223" };
private static void Main(string[] args)
{
string[,] phonesNames = new string[2, names.Length];
for (var i = 0; i < names.Length; i++)
{
phonesNames[0, i] = names[i];
phonesNames[1, i] = phones[i];
}
// loop through all columns
for (int i = 0; i < phonesNames.GetLength(1); i++)
{
var phoneName = GetColumn(phonesNames, i);
Console.WriteLine(string.Join(" ", phoneName));
}
}
static string[] GetColumn(string[,] matrix, int columnNumber)
{
return Enumerable.Range(0, matrix.GetLength(0))
.Select(x => matrix[x, columnNumber])
.ToArray();
}
}
Output:
xaw 535-4213
Tommy 535-0421
Alan 722-352
Sergio 070-3531
Adam 343-2324
Pablo 344-2223
Visualize PhoneNames 2D Array:
To access a specific cell, you simply use:
Console.WriteLine(phonesNames[0,2]); // Alan
To access a whole column, e.g. 4th column:
var column4 = GetColumn(phonesNames, 4);
Console.WriteLine(string.Join(" ", column4));
// output = Adam 343-2324

Connect element in distinct array using recursion

if I have two array
A:[A,B]
B:[1,2,3]
how can I create a string List like [A_1, A_2, A_3, B_1, B_2, B_3]
the number of array is not regular, it's maybe have 3 more
A:[A,B]
B:[1,2,3]
C:[w,x,y,z]
D:[m,n]
E:[p,q,r]
can I use recursive to solve it?

So, we define a functions Mergethat takes lists of list of stings and merges them into the string enumerable you want
static void Main(string[] args)
{
var a = new[] { "A", "B" };
var b = new[] { "1", "2", "3" };
var c = new[] { "x", "y", "z", "w" };
var result = Merge(a, b, c);
foreach (var r in result)
{
Console.WriteLine(r);
}
}
public static IList<string> Merge(params IEnumerable<string>[] lists)
{
return Merge((IEnumerable<IEnumerable<string>>) lists);
}
public static IList<string> Merge(IEnumerable<IEnumerable<string>> lists)
{
var retval = new List<string>();
var first = lists.FirstOrDefault();
if (first != null)
{
var result = Merge(lists.Skip(1));
if (result.Count > 0)
{
foreach (var x in first)
{
retval.AddRange(result.Select(y => string.Format("{0}_{1}", x, y)));
}
}
else
{
retval.AddRange(first);
}
}
return retval;
}
we can also improve this, if you use Lists as inputs
public static IList<string> Merge(params IList<string>[] lists)
{
return Merge((IList<IList<string>>) lists);
}
public static IList<string> Merge(IList<IList<string>> lists, int offset = 0)
{
if (offset >= lists.Count)
return new List<string>();
var current = lists[offset];
if (offset + 1 == lists.Count) // last entry in lists
return current;
var retval = new List<string>();
var merged = Merge(lists, offset + 1);
foreach (var x in current)
{
retval.AddRange(merged.Select(y => string.Format("{0}_{1}", x, y)));
}
return retval;
}

This is simple iterating over n-ary dimension - no need for recursion for that, just array to store indexes.
static void Iterate(int[] iterators, ArrayList[] arrays) {
for (var j = iterators.Length - 1; j >= 0; j--) {
iterators[j]++;
if (iterators[j] == arrays[j].Count) {
if (j == 0) {
break;
}
iterators[j] = 0;
} else {
break;
}
}
}
static IList<string> Merge(ArrayList[] arrays) {
List<string> result = new List<string>();
int[] iterators = new int[arrays.Length];
while (iterators[0] != arrays[0].Count) {
var builder = new StringBuilder(20);
for(var index = 0; index < arrays.Length; index++) {
if (index > 0) {
builder.Append("_");
}
builder.Append(arrays[index][iterators[index]]);
}
result.Add(builder.ToString());
Iterate(iterators, arrays);
}
return result;
}
static void Main(string[] args) {
var list1 = new ArrayList();
var list2 = new ArrayList();
var list3 = new ArrayList();
list1.Add(1);
list1.Add(2);
list2.Add("a");
list2.Add("b");
list3.Add("x");
list3.Add("y");
list3.Add("z");
var result = Merge(new[] { list1, list2, list3 });
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace arrconn {
class Program {
static string[] conn(params Array[] arrs) {
if(arrs.Length == 0) return new string[0];
if(arrs.Length == 1) {
string[] result = new string[arrs[0].Length];
for(int i = 0; i < result.Length; i++)
result[i] = arrs[0].GetValue(i).ToString();
return result; }
else {
string[] result = new string[arrs[0].Length*arrs[1].Length];
for(int i = 0; i < arrs[0].Length; i++)
for(int j = 0; j < arrs[1].Length; j++)
result[i*arrs[1].Length+j] = string.Format("{0}_{1}", arrs[0].GetValue(i), arrs[1].GetValue(j));
if(arrs.Length == 2) return result;
Array[] next = new Array[arrs.Length-1];
next[0] = result; Array.Copy(arrs, 2, next, 1, next.Length-1);
return conn(next);
}
}
static void Main(string[] args) {
foreach(string s in conn(
new string[] { "A", "B" },
new int[] { 1, 2, 3 },
new string[] { "x" },
new string[] { "$", "%", "#" }))
Console.WriteLine(s);
Console.Read();
}
}
}

I guess your input are like this:
var A = ["A","B"];
var B = [1,2,3];
var C = ["x","y","z","w"];
And what you want to obtain is:
var result = ["A_1_x", "A_1_y",...
"A_2_x", "A_2_y",...
"A_3_x", "A_3_y",...
"B_1_x", "B_1_y",...
...
..., "B_3_z", "B_3_w"];
We'll be working with IEnumerable as it will simplify the work for us and give us access to the yield keyword.
First, let's take care of the case where we only concataining two collections:
IEnumerable<string> ConcatEnumerables(IEnumerable<object> first, IEnumerable<object> second)
{
foreach (var x in first)
{
foreach (var y in second)
{
yield return x.ToString() + "_" + y.ToString();
}
}
}
Then we can recursively takle any number of collections:
IEnumerable<string> ConcatEnumerablesRec(IEnumerable<IEnumerable<object>> enums)
{
//base cases
if(!enums.Any())
{
return Enumerable.Empty<string>();
}
if (enums.Count() == 1)
{
return enums.First().Select(o => o.ToString());
}
//recursively solve the problem
return ConcatEnumerables(enums.First(), ConcatEnumerablesRec(enums.Skip(1));
}
Now you just need to call ToArray on the result if you really need an array as your output.
string[] Concatenator(params object[][] parameters)
{
return ConcatEnumerablesRec(parameters).ToArray();
}

This should do the trick. Note that the input sequences do not have to be arrays - they can be any type that implements IEnumerable<>.
Also note that we have to case sequences of value types to sequences of <object> so that they are assignable to IEnumerable<object>.
Here's the compilable Console app demo code:
using System;
using System.Collections.Generic;
using System.Linq;
namespace Demo
{
internal static class Program
{
static void Main()
{
string[] a = {"A", "B", "C", "D"};
var b = Enumerable.Range(1, 3); // <-- See how it doesn't need to be an array.
char[] c = {'X', 'Y', 'Z'};
double[] d = {-0.1, -0.2};
var sequences = new [] { a, b.Cast<object>(), c.Cast<object>(), d.Cast<object>() };
Console.WriteLine(string.Join("\n", Combine("", sequences)));
}
public static IEnumerable<string> Combine(string prefix, IEnumerable<IEnumerable<object>> sequences)
{
foreach (var item in sequences.First())
{
string current = (prefix == "") ? item.ToString() : prefix + "_" + item;
var remaining = sequences.Skip(1);
if (!remaining.Any())
{
yield return current;
}
else
{
foreach (var s in Combine(current, remaining))
yield return s;
}
}
}
}
}

Move elements from one arraylist to another arraylist asp .net

I have two arraylist
public ArrayList myA = new ArrayList();
public ArrayList myB = new ArrayList();
When comes a new value in myA, delete the old content of myB, moving the old content from myA to myB and in myA have the new value
For example:
myA("value1","value2","value3");
myB("","","");
Come the new values:
myA("value4","value5","value6");
myB("value1","value2","value3");
Come another values:
myA("value7","value8","value9");
myB("value4","value5","value6");
Please help me

If I understood you correctly this should do the work
// Initial values
ArrayList myA = new ArrayList() { "value1", "value2", "value3" };
ArrayList myB = new ArrayList() { "", "", "" };
// New values
ArrayList myC = new ArrayList() { "value4", "value5", "value6" };
// Clear the old values from myB and add the old values of myA to myB
myB.Clear();
myB.AddRange(myA);
// Clear the old values from mya and add the new values to myA
myA.Clear();
myA.AddRange(myC);

using System.IO;
using System;
using System.Collections.Generic;
public class ArrayWithBackup : List<String>
{
List<String> arrayWithBackup;
List<String> backupArray;
public ArrayWithBackup()
{
arrayWithBackup = new List<string>();
}
public void AddStrings(List<String> inputs)
{
if (backupArray != null && backupArray.Count > 0)
backupArray.Clear();
backupArray = new List<string>(arrayWithBackup);
arrayWithBackup.Clear();
for (int i = 0; i < inputs.Count; ++i)
{
arrayWithBackup.Add(inputs[i]);
}
}
public void PrintArray()
{
Console.WriteLine("Array contains:");
for(int i = 0; i < arrayWithBackup.Count; ++i)
Console.WriteLine("Index {0}: {1}", i, arrayWithBackup[i]);
}
public void PrintBackupArray()
{
Console.WriteLine("BackupArray contains:");
for (int i = 0; i < backupArray.Count; ++i)
Console.WriteLine("Index {0}: {1}", i, backupArray[i]);
}
public List<String> GetArray()
{
return arrayWithBackup;
}
public List<String> GetBackupArray()
{
return backupArray;
}
}
public class Test
{
static void Main(string[] args)
{
ArrayWithBackup awb = new ArrayWithBackup();
List<String> inputs = new List<String>();
inputs.Add("one");
inputs.Add("two");
inputs.Add("three");
awb.AddStrings(inputs);
inputs.Clear();
inputs.Add("four");
inputs.Add("five");
inputs.Add("six");
awb.AddStrings(inputs);
awb.PrintArray();
awb.PrintBackupArray();
}
}
//Output:
//Array contains:
//Index 0: four
//Index 1: five
//Index 2: six
//BackupArray contains:
//Index 0: one
//Index 1: two
//Index 2: three

C# Permutation of an array of arraylists?

I have an ArrayList[] myList and I am trying to create a list of all the permutations of the values in the arrays.
EXAMPLE: (all values are strings)
myList[0] = { "1", "5", "3", "9" };
myList[1] = { "2", "3" };
myList[2] = { "93" };
The count of myList can be varied so its length is not known beforehand.
I would like to be able to generate a list of all the permutations similar to the following (but with some additional formatting).
1 2 93
1 3 93
5 2 93
5 3 93
3 2 93
3 3 93
9 2 93
9 3 93
Does this make sense of what I am trying to accomplish? I can't seem to come up with a good method for doing this, (if any).
Edit:
I am not sure if recursion would interfere with my desire to format the output in my own manner. Sorry I did not mention before what my formatting was.
I want to end up building a string[] array of all the combinations that follows the format like below:
for the "1 2 93" permutation
I want the output to be "val0=1;val1=2;val2=93;"
I will experiment with recursion for now. Thank you DrJokepu

I'm surprised nobody posted the LINQ solution.
from val0 in new []{ "1", "5", "3", "9" }
from val1 in new []{ "2", "3" }
from val2 in new []{ "93" }
select String.Format("val0={0};val1={1};val2={2}", val0, val1, val2)

Recursive solution
static List<string> foo(int a, List<Array> x)
{
List<string> retval= new List<string>();
if (a == x.Count)
{
retval.Add("");
return retval;
}
foreach (Object y in x[a])
{
foreach (string x2 in foo(a + 1, x))
{
retval.Add(y.ToString() + " " + x2.ToString());
}
}
return retval;
}
static void Main(string[] args)
{
List<Array> myList = new List<Array>();
myList.Add(new string[0]);
myList.Add(new string[0]);
myList.Add(new string[0]);
myList[0] = new string[]{ "1", "5", "3", "9" };
myList[1] = new string[] { "2", "3" };
myList[2] = new string[] { "93" };
foreach (string x in foo(0, myList))
{
Console.WriteLine(x);
}
Console.ReadKey();
}
Note that it would be pretty easy to return a list or array instead of a string by changing the return to be a list of lists of strings and changing the retval.add call to work with a list instead of using concatenation.
How it works:
This is a classic recursive algorithm. The base case is foo(myList.Count, myList), which returns a List containing one element, the empty string. The permutation of a list of n string arrays s1, s2, ..., sN is equal to every member of sA1 prefixed to the permutation of n-1 string arrays, s2, ..., sN. The base case is just there to provide something for each element of sN to be concatenated to.

I recently ran across a similar problem in a project of mine and stumbled on this question. I needed a non-recursive solution that could work with lists of arbitrary objects. Here's what I came up with. Basically I'm forming a list of enumerators for each of the sub-lists and incrementing them iteratively.
public static IEnumerable<IEnumerable<T>> GetPermutations<T>(IEnumerable<IEnumerable<T>> lists)
{
// Check against an empty list.
if (!lists.Any())
{
yield break;
}
// Create a list of iterators into each of the sub-lists.
List<IEnumerator<T>> iterators = new List<IEnumerator<T>>();
foreach (var list in lists)
{
var it = list.GetEnumerator();
// Ensure empty sub-lists are excluded.
if (!it.MoveNext())
{
continue;
}
iterators.Add(it);
}
bool done = false;
while (!done)
{
// Return the current state of all the iterator, this permutation.
yield return from it in iterators select it.Current;
// Move to the next permutation.
bool recurse = false;
var mainIt = iterators.GetEnumerator();
mainIt.MoveNext(); // Move to the first, succeeds; the main list is not empty.
do
{
recurse = false;
var subIt = mainIt.Current;
if (!subIt.MoveNext())
{
subIt.Reset(); // Note the sub-list must be a reset-able IEnumerable!
subIt.MoveNext(); // Move to the first, succeeds; each sub-list is not empty.
if (!mainIt.MoveNext())
{
done = true;
}
else
{
recurse = true;
}
}
}
while (recurse);
}
}

You could use factoradics to generate the enumeration of permutations. Try this article on MSDN for an implementation in C#.

This will work no matter how many arrays you add to your myList:
static void Main(string[] args)
{
string[][] myList = new string[3][];
myList[0] = new string[] { "1", "5", "3", "9" };
myList[1] = new string[] { "2", "3" };
myList[2] = new string[] { "93" };
List<string> permutations = new List<string>(myList[0]);
for (int i = 1; i < myList.Length; ++i)
{
permutations = RecursiveAppend(permutations, myList[i]);
}
//at this point the permutations variable contains all permutations
}
static List<string> RecursiveAppend(List<string> priorPermutations, string[] additions)
{
List<string> newPermutationsResult = new List<string>();
foreach (string priorPermutation in priorPermutations)
{
foreach (string addition in additions)
{
newPermutationsResult.Add(priorPermutation + ":" + addition);
}
}
return newPermutationsResult;
}
Note that it's not really recursive. Probably a misleading function name.
Here is a version that adheres to your new requirements. Note the section where I output to console, this is where you can do your own formatting:
static void Main(string[] args)
{
string[][] myList = new string[3][];
myList[0] = new string[] { "1", "5", "3", "9" };
myList[1] = new string[] { "2", "3" };
myList[2] = new string[] { "93" };
List<List<string>> permutations = new List<List<string>>();
foreach (string init in myList[0])
{
List<string> temp = new List<string>();
temp.Add(init);
permutations.Add(temp);
}
for (int i = 1; i < myList.Length; ++i)
{
permutations = RecursiveAppend(permutations, myList[i]);
}
//at this point the permutations variable contains all permutations
foreach (List<string> list in permutations)
{
foreach (string item in list)
{
Console.Write(item + ":");
}
Console.WriteLine();
}
}
static List<List<string>> RecursiveAppend(List<List<string>> priorPermutations, string[] additions)
{
List<List<string>> newPermutationsResult = new List<List<string>>();
foreach (List<string> priorPermutation in priorPermutations)
{
foreach (string addition in additions)
{
List<string> priorWithAddition = new List<string>(priorPermutation);
priorWithAddition.Add(addition);
newPermutationsResult.Add(priorWithAddition);
}
}
return newPermutationsResult;
}

What you are asking for is called the Cartesian Product. Once you know what its called, there are several similar questions on Stack Overflow. They all seem to end up pointing to an answer which ended up written as a blog post:
http://blogs.msdn.com/b/ericlippert/archive/2010/06/28/computing-a-cartesian-product-with-linq.aspx

Non-recursive solution:
foreach (String s1 in array1) {
foreach (String s2 in array2) {
foreach (String s3 in array3) {
String result = s1 + " " + s2 + " " + s3;
//do something with the result
}
}
}
Recursive solution:
private ArrayList<String> permute(ArrayList<ArrayList<String>> ar, int startIndex) {
if (ar.Count == 1) {
foreach(String s in ar.Value(0)) {
ar.Value(0) = "val" + startIndex + "=" + ar.Value(0);
return ar.Value(0);
}
ArrayList<String> ret = new ArrayList<String>();
ArrayList<String> tmp1 ar.Value(0);
ar.remove(0);
ArrayList<String> tmp2 = permute(ar, startIndex+1);
foreach (String s in tmp1) {
foreach (String s2 in tmp2) {
ret.Add("val" + startIndex + "=" + s + " " + s2);
}
}
return ret;
}

Here is a generic recursive function that I wrote (and an overload that may be convenient to call):
Public Shared Function GetCombinationsFromIEnumerables(ByRef chain() As Object, ByRef IEnumerables As IEnumerable(Of IEnumerable(Of Object))) As List(Of Object())
Dim Combinations As New List(Of Object())
If IEnumerables.Any Then
For Each v In IEnumerables.First
Combinations.AddRange(GetCombinationsFromIEnumerables(chain.Concat(New Object() {v}).ToArray, IEnumerables.Skip(1)).ToArray)
Next
Else
Combinations.Add(chain)
End If
Return Combinations
End Function
Public Shared Function GetCombinationsFromIEnumerables(ByVal ParamArray IEnumerables() As IEnumerable(Of Object)) As List(Of Object())
Return GetCombinationsFromIEnumerables(chain:=New Object() {}, IEnumerables:=IEnumerables.AsEnumerable)
End Function
And the equivalent in C#:
public static List<object[]> GetCombinationsFromIEnumerables(ref object[] chain, ref IEnumerable<IEnumerable<object>> IEnumerables)
{
List<object[]> Combinations = new List<object[]>();
if (IEnumerables.Any) {
foreach ( v in IEnumerables.First) {
Combinations.AddRange(GetCombinationsFromIEnumerables(chain.Concat(new object[] { v }).ToArray, IEnumerables.Skip(1)).ToArray);
}
} else {
Combinations.Add(chain);
}
return Combinations;
}
public static List<object[]> GetCombinationsFromIEnumerables(params IEnumerable<object>[] IEnumerables)
{
return GetCombinationsFromIEnumerables(chain = new object[], IEnumerables = IEnumerables.AsEnumerable);
}
Easy to use:
Dim list1 = New String() {"hello", "bonjour", "hallo", "hola"}
Dim list2 = New String() {"Erwin", "Larry", "Bill"}
Dim list3 = New String() {"!", ".."}
Dim result = MyLib.GetCombinationsFromIEnumerables(list1, list2, list3)
For Each r In result
Debug.Print(String.Join(" "c, r))
Next
or in C#:
object list1 = new string[] {"hello","bonjour","hallo","hola"};
object list2 = new string[] {"Erwin", "Larry", "Bill"};
object list3 = new string[] {"!",".."};
object result = MyLib.GetCombinationsFromIEnumerables(list1, list2, list3);
foreach (r in result) {
Debug.Print(string.Join(' ', r));
}

Here is a version which uses very little code, and is entirely declarative
public static IEnumerable<IEnumerable<T>> GetPermutations<T>(IEnumerable<T> collection) where T : IComparable
{
if (!collection.Any())
{
return new List<IEnumerable<T>>() {Enumerable.Empty<T>() };
}
var sequence = collection.OrderBy(s => s).ToArray();
return sequence.SelectMany(s => GetPermutations(sequence.Where(s2 => !s2.Equals(s))).Select(sq => (new T[] {s}).Concat(sq)));
}

class Program
{
static void Main(string[] args)
{
var listofInts = new List<List<int>>(3);
listofInts.Add(new List<int>{1, 2, 3});
listofInts.Add(new List<int> { 4,5,6 });
listofInts.Add(new List<int> { 7,8,9,10 });
var temp = CrossJoinLists(listofInts);
foreach (var l in temp)
{
foreach (var i in l)
Console.Write(i + ",");
Console.WriteLine();
}
}
private static IEnumerable<List<T>> CrossJoinLists<T>(IEnumerable<List<T>> listofObjects)
{
var result = from obj in listofObjects.First()
select new List<T> {obj};
for (var i = 1; i < listofObjects.Count(); i++)
{
var iLocal = i;
result = from obj in result
from obj2 in listofObjects.ElementAt(iLocal)
select new List<T>(obj){ obj2 };
}
return result;
}
}

Here's a non-recursive, non-Linq solution. I can't help feeling like I could have less looping and calculate the positions with division and modulo, but can't quite wrap my head around that.
static void Main(string[] args)
{
//build test list
List<string[]> myList = new List<string[]>();
myList.Add(new string[0]);
myList.Add(new string[0]);
myList.Add(new string[0]);
myList[0] = new string[] { "1", "2", "3"};
myList[1] = new string[] { "4", "5" };
myList[2] = new string[] { "7", "8", "9" };
object[][] xProds = GetProducts(myList.ToArray());
foreach(object[] os in xProds)
{
foreach(object o in os)
{
Console.Write(o.ToString() + " ");
}
Console.WriteLine();
}
Console.ReadKey();
}
static object[][] GetProducts(object[][] jaggedArray){
int numLists = jaggedArray.Length;
int nProducts = 1;
foreach (object[] oArray in jaggedArray)
{
nProducts *= oArray.Length;
}
object[][] productAry = new object[nProducts][];//holds the results
int[] listIdxArray = new int[numLists];
listIdxArray.Initialize();
int listPtr = 0;//point to current list
for(int rowcounter = 0; rowcounter < nProducts; rowcounter++)
{
//create a result row
object[] prodRow = new object[numLists];
//get values for each column
for(int i=0;i<numLists;i++)
{
prodRow[i] = jaggedArray[i][listIdxArray[i]];
}
productAry[rowcounter] = prodRow;
//move the list pointer
//possible states
// 1) in a list, has room to move down
// 2) at bottom of list, can move to next list
// 3) at bottom of list, no more lists left
//in a list, can move down
if (listIdxArray[listPtr] < (jaggedArray[listPtr].Length - 1))
{
listIdxArray[listPtr]++;
}
else
{
//can move to next column?
//move the pointer over until we find a list, or run out of room
while (listPtr < numLists && listIdxArray[listPtr] >= (jaggedArray[listPtr].Length - 1))
{
listPtr++;
}
if (listPtr < listIdxArray.Length && listIdxArray[listPtr] < (jaggedArray[listPtr].Length - 1))
{
//zero out the previous stuff
for (int k = 0; k < listPtr; k++)
{
listIdxArray[k] = 0;
}
listIdxArray[listPtr]++;
listPtr = 0;
}
}
}
return productAry;
}

One of the problems I encountred when I was doing this for a very large amount of codes was that with the example brian was given I actually run out of memory. To solve this I used following code.
static void foo(string s, List<Array> x, int a)
{
if (a == x.Count)
{
// output here
Console.WriteLine(s);
}
else
{
foreach (object y in x[a])
{
foo(s + y.ToString(), x, a + 1);
}
}
}
static void Main(string[] args)
{
List<Array> a = new List<Array>();
a.Add(new string[0]);
a.Add(new string[0]);
a.Add(new string[0]);
a[0] = new string[] { "T", "Z" };
a[1] = new string[] { "N", "Z" };
a[2] = new string[] { "3", "2", "Z" };
foo("", a, 0);
Console.Read();
}

private static void GetP(List<List<string>> conditions, List<List<string>> combinations, List<string> conditionCombo, List<string> previousT, int selectCnt)
{
for (int i = 0; i < conditions.Count(); i++)
{
List<string> oneField = conditions[i];
for (int k = 0; k < oneField.Count(); k++)
{
List<string> t = new List<string>(conditionCombo);
t.AddRange(previousT);
t.Add(oneField[k]);
if (selectCnt == t.Count )
{
combinations.Add(t);
continue;
}
GetP(conditions.GetRange(i + 1, conditions.Count - 1 - i), combinations, conditionCombo, t, selectCnt);
}
}
}
List<List<string>> a = new List<List<string>>();
a.Add(new List<string> { "1", "5", "3", "9" });
a.Add(new List<string> { "2", "3" });
a.Add(new List<string> { "93" });
List<List<string>> result = new List<List<string>>();
GetP(a, result, new List<string>(), new List<string>(), a.Count);
Another recursive function.