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Sort Array on on Value Difference

I Have An Array,for example
string[] stArr= new string[5] { "1#3", "19#24", "10#12", "13#18", "20#21" };
i want to sort this array on
3-1=2;
24-19=5;
12-10=2;
18-13=5;
21-20=1;
and the sorting result should be like
string[] stArr= new string[5] { "20#21", "1#3", "10#12", "13#18", "20#21" };
I have to find the solution for all possible cases.
1>length of the array is not fixed(element in the array)
2>y always greater than x e.g x#y
3> i can not use list

You can use LINQ:
var sorted = stArr.OrderBy(s => s.Split('#')
.Select(n => Int32.Parse(n))
.Reverse()
.Aggregate((first,second) => first - second));
For Your Case:
stArr = stArr.OrderBy(s => s.Split('#')
.Select(n => Int32.Parse(n))
.Reverse()
.Aggregate((first,second) => first - second)).ToArray();

try this
string[] stArr = new string[5] { "1#3", "19#24", "10#12", "13#18", "20#21" };
Array.Sort(stArr, new Comparison<string>(compare));
int compare(string z, string t)
{
var xarr = z.Split('#');
var yarr = t.Split('#');
var x1 = int.Parse(xarr[0]);
var y1 = int.Parse(xarr[1]);
var x2 = int.Parse(yarr[0]);
var y2 = int.Parse(yarr[1]);
return (y1 - x1).CompareTo(y2 - x2);
}

Solving this problem is identical to solving any other sorting problem where the order is to be specified by your code - you have to write a custom comparison method, and pass it to the built-in sorter.
In your situation, it means writing something like this:
private static int FindDiff(string s) {
// Split the string at #
// Parse both sides as int
// return rightSide-leftSide
}
private static int CompareDiff(string a, string b) {
return FindDiff(a).CompareTo(FindDiff(b));
}
public static void Main() {
... // Prepare your array
string[] stArr = ...
Array.Sort(stArr, CompareDiff);
}
This approach uses Array.Sort overload with the Comparison<T> delegate implemented in the CompareDiff method. The heart of the solution is the FindDiff method, which takes a string, and produces a numeric value which must be used for comparison.

you can try the following ( using traditional way)
public class Program
{
public static void Main()
{
string[] strArr= new string[5] { "1#3", "19#24", "10#12", "13#18", "20#21" };
var list = new List<Item>();
foreach(var item in strArr){
list.Add(new Item(item));
}
strArr = list.OrderBy(t=>t.Sort).Select(t=>t.Value).ToArray();
foreach(var item in strArr)
Console.WriteLine(item);
}
}
public class Item
{
public Item(string str)
{
var split = str.Split('#');
A = Convert.ToInt32(split[0]);
B = Convert.ToInt32(split[1]);
}
public int A{get; set;}
public int B{get; set;}
public int Sort { get { return Math.Abs(B - A);}}
public string Value { get { return string.Format("{0}#{1}",B,A); }}
}
here a working demo
hope it will help you

Without LINQ and Lists :) Old School.
static void Sort(string [] strArray)
{
try
{
string[] order = new string[strArray.Length];
string[] sortedarray = new string[strArray.Length];
for (int i = 0; i < strArray.Length; i++)
{
string[] values = strArray[i].ToString().Split('#');
int index=int.Parse(values[1].ToString()) - int.Parse(values[0].ToString());
order[i] = strArray[i].ToString() + "," + index;
}
for (int i = 0; i < order.Length; i++)
{
string[] values2 = order[i].ToString().Split(',');
if (sortedarray[int.Parse(values2[1].ToString())-1] == null)
{
sortedarray[int.Parse(values2[1].ToString())-1] = values2[0].ToString();
}
else
{
if ((int.Parse(values2[1].ToString())) >= sortedarray.Length)
{
sortedarray[(int.Parse(values2[1].ToString())-1) - 1] = values2[0].ToString();
}
else if ((int.Parse(values2[1].ToString())) < sortedarray.Length)
{
sortedarray[(int.Parse(values2[1].ToString())-1) + 1] = values2[0].ToString();
}
}
}
for (int i = 0; i < sortedarray.Length; i++)
{
Console.WriteLine(sortedarray[i]);
}
Console.Read();
}
catch (Exception ex)
{
throw;
}
finally
{
}

Locating items in List whether they occur more than once in C#

In addition to the question: Get List<> element position in c# using LINQ
First of all, let me explaing why I do what I do :)
I'm trying to encrypt a string into a one-line code which holds how many times a letter is used in the string and also with its positions. By this method, I'll be able to decrypt the code and get(reproduce) the full text again. Let's say myString is "How are you today". I'll encrypt it like
o3[1,9,13]," "3[3,7,11],a2[4,15],y2[9,17],H1[0],w1[2],r1[5],e1[6],u1[10],t1[12],d1[14],?[18]
I know it looks odd but think about working on bigger strings like e-books. This could handle all the text in one or two lines.
The encryption is not about the security, it's just about holding big datas in smaller spaces.
In my code, I can convert the string into list, count how many times a letter is used but I can't define the positions of the letters when they occur more than once.
private void btnKoda_Click(object sender, EventArgs e)
{
var yazi = txtYazi.Text;
List<char> liste = yazi.ToList();
List<string> tut = new List<string>();
foreach (char harf in liste)
{
for (int i = 0; i < liste.Count; i++)
{
char ekle = liste[i];
tut.Add(ekle.ToString());
}
foreach (var karakter in tut)
{
txtKod.Text += karakter;
}
// holds statics
var istatistik =
from c in tut
group c by c into g
select new { g.Key, say = g.Count() };
var enCok =
from giris in istatistik
orderby giris.say descending
select giris;
foreach (var giris in enCok)
{
txtHarfler.Text += string.Format("{0}: {1}\r\n", giris.Key, giris.say);
}
break;
}

Not sure what's going on in your code, but here's how I would do it:
private void button1_Click(object sender, EventArgs e)
{
Dictionary<Char, Encoding> dct = new Dictionary<char, Encoding>();
string data = "How are you today";
for(int i = 0; i < data.Length; i++)
{
Char C = data[i];
if (!dct.ContainsKey(C))
{
dct.Add(C, new Encoding(C));
}
dct[C].AddOccurence(i);
}
StringBuilder SB = new StringBuilder();
foreach(Encoding enc in dct.Values)
{
if (SB.Length == 0)
{
SB.Append(enc.ToString());
}
else
{
SB.Append("," + enc.ToString());
}
}
Console.WriteLine(SB.ToString());
}
Here's the Encoding class:
public class Encoding
{
private Char _C;
private List<int> _Positions;
private Encoding() {}
public Encoding(Char C)
{
this._C = C;
this._Positions = new List<int>();
}
public Char Character
{
get
{
return _C;
}
}
public int Count
{
get
{
return _Positions.Count;
}
}
public int[] Occurences
{
get
{
return _Positions.ToArray();
}
}
public override string ToString()
{
string[] values = Array.ConvertAll(this.Occurences.ToArray(), x => x.ToString());
return this.Character.ToString() + this.Count.ToString() + "[" + String.Join(",", values) + "]";
}
public void AddOccurence(int position)
{
this._Positions.Add(position);
}
}
Original String:
How are you today
Output:
H1[0],o3[1,9,13],w1[2], 3[3,7,11],a2[4,15],r1[5],e1[6],y2[8,16],u1[10],t1[12],d1[14]

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;
}
}
}
}
}

How do i create the functions of List<float> in the options file?

I have in the options file two functions GetKey and SetKey.
I set a key then in the settings_file.txt it will look like:
text = hello where text is the key then = and hello is the value for the current key.
Now i need to add another two functions the first one is type of List that get a string and return a List
And a another function that get a Key and a List.
So this is the first two functions allready working GetKey and SetKey:
/*----------------------------------------------------------------
* Module Name : OptionsFile
* Description : Saves and retrievs application options
* Author : Danny
* Date : 10/02/2010
* Revision : 1.00
* --------------------------------------------------------------*/
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.IO;
using System.Configuration;
/*
* Introduction :
*
* This module helps in saving application options
*
*
* Typical file could look like this:
* user_color=Red
* time_left=30
*
*
*
*
*
* */
namespace DannyGeneral
{
class OptionsFile
{
/*----------------------------------------
* P R I V A T E V A R I A B L E S
* ---------------------------------------*/
/*---------------------------------
* P U B L I C M E T H O D S
* -------------------------------*/
string path_exe;
string temp_settings_file;
string temp_settings_dir;
string Options_File;
StreamWriter sw;
StreamReader sr;
/*----------------------------------------------------------
* Function : OptionsFile
* Description : Constructor
* Parameters : file_name is the name of the file to use
* Return : none
* --------------------------------------------------------*/
public OptionsFile(string settings)
{
if (!File.Exists(settings))
{
if (!Directory.Exists(Path.GetDirectoryName(settings)))
{
Directory.CreateDirectory(Path.GetDirectoryName(settings));
}
File.Create(settings).Close();
}
path_exe = Path.GetDirectoryName(Application.LocalUserAppDataPath);
Options_File = settings;
}
/*----------------------------------------------------------
* Function : GetKey
* Description : gets the value of the key.
* Parameters : key
* Return : value of the key if key exist, null if not exist
* --------------------------------------------------------*/
public string GetKey(string key)
{
// string value_of_each_key;
string key_of_each_line;
string line;
int index;
string key_value;
key_value = null;
sr = new StreamReader(Options_File);
while (null != (line = sr.ReadLine()))
{
index = line.IndexOf("=");
// value_of_each_key = line.Substring(index+1);
if (index >= 1)
{
key_of_each_line = line.Substring(0, index);
if (key_of_each_line == key)
{
key_value = line.Substring(key.Length + 1);
}
}
else
{
}
}
sr.Close();
return key_value;
}
/*----------------------------------------------------------
* Function : SetKey
* Description : sets a value to the specified key
* Parameters : key and a value
* Return : none
* --------------------------------------------------------*/
public void SetKey(string key , string value)
{
bool key_was_found_inside_the_loop;
string value_of_each_key;
string key_of_each_line ;
string line;
int index;
key_was_found_inside_the_loop = false;
temp_settings_file = "\\temp_settings_file.txt";
temp_settings_dir = path_exe + #"\temp_settings";
if (!Directory.Exists(temp_settings_dir))
{
Directory.CreateDirectory(temp_settings_dir);
}
sw = new StreamWriter(temp_settings_dir+temp_settings_file);
sr = new StreamReader(Options_File);
while (null != (line = sr.ReadLine()))
{
index = line.IndexOf("=");
key_of_each_line = line.Substring(0, index);
value_of_each_key = line.Substring( index + 1);
// key_value = line.Substring(0,value.Length);
if (key_of_each_line == key)
{
sw.WriteLine(key + " = " + value);
key_was_found_inside_the_loop = true;
}
else
{
sw.WriteLine(key_of_each_line+"="+value_of_each_key);
}
}
if (!key_was_found_inside_the_loop)
{
sw.WriteLine(key + "=" + value);
}
sr.Close();
sw.Close();
File.Delete(Options_File);
File.Move(temp_settings_dir + temp_settings_file, Options_File);
return;
}
After this two functions i did:
public List<float> GetListFloatKey(string keys)
{
int j;
List<float> t;
t = new List<float>();
int i;
for (i = 0; ; i++)
{
j = Convert.ToInt32(GetKey((keys + i).ToString()));
if (j == 0)
{
break;
}
else
{
t.Add(j);
}
}
if (t.Count == 0)
return null;
else
return t;
}
public void SetListFloatKey(string key, List<float> Values)
{
int i;
for (i = 0; i < Values.Count; i++)
{
string indexed_key;
indexed_key = string.Format("{0}{1}", key, i);
// indexed_key = Key + i.ToString();
SetKey(indexed_key, Values[i].ToString());
}
}
But they are not good.
The last one the SetListFloatKey when i put a List in it the result in the text file settings_file.txt is for exmaple:
coordinates01 = 123
coordinates02 = 144
coordinates03 = 145
For every cell/index in the List i get its making a key. What i need is that the List i get will have one key the format in the text file should be like this:
coordinates = 123,144,145......and so on one key and then all the values from the List i get.
Then in the GetListFloatKey i need re format the values according to the key for example coordinates and return a List with the values in index 0 123 in 1 144 in 2 145 and so on....
The qustion if the function the way im doing them are good in the way im using in both GetKey and SetKey ? And how do i format and re format the values ?

At the moment you are calling SetKey within SetListFloatKey for every item in the list. Instead, you need to build a string and call it once, along the lines of (basic testing done):
public static void SetListFloatKey(string key, List<float> Values)
{
StringBuilder sb = new StringBuilder();
foreach (float value in Values)
{
sb.AppendFormat("{0},", value);
}
SetKey(key, sb.ToString());
}
Note I am getting lazy here - the last item will have a comma after it. Then when loading the list:
public static List<float> GetListFloatKey(string keys)
{
List<float> result = new List<float>();
string s = GetKey(keys);
string[] items = s.Split(new char[] { ',' });
float f;
foreach (string item in items)
{
if (float.TryParse(item, out f))
result.Add(f);
}
return result;
}
However, given you are reading and writing an options file, you might want to investigate options around serializing your objects to and from files.
EDIT There are a few ways you can get rid of the extra comma. One way is to not put it in in the first place...
string sep = "";
foreach (float value in Values)
{
sb.AppendFormat("{0}{1}", sep, value);
if (sep == "") sep = ",";
}
...and another is to exclude it in the call to SetKey...
foreach (float value in Values)
{
sb.AppendFormat(",{0}", value);
}
SetKey(key, sb.ToString().Substring(1));
..note that in both of these cases I moved the comma to the start to make life easier. Alternatively, you could store the numbers in an array and use Array.Join.

I think that you are wasting too much time thinking about how to format the file each time you make a change, you are also causing a lot of file overhead each time you check for a key.
Consider using a class like
public class Options
{
public static string FILENAME = #"C:\Test\testfile.txt";
public List<KeyValuePair<string, string>> OrderedKeys { get; set; }
public Dictionary<string, KeyValuePair<string, string>> Pairs { get; set; }
public string GetKey(string key)
{
return this.Pairs[key].Value;
}
public void SetKey(string key, string value)
{
if(this.Pairs.ContainsKey(key))
{
KeyValuePair<string, string> pair = new KeyValuePair<string, string>(key, value);
this.OrderedKeys.Insert(this.OrderedKeys.IndexOf(this.Pairs[key]), pair);
this.Pairs[key] = pair;
}
}
public Options()
{
LoadFile();
}
~Options()
{
WriteFile();
}
private void LoadFile()
{
Regex regex = new Regex(#"(?<key>\S*?)\s*=\s*(?<val>\S*?)\s*\r\n");
MatchCollection matches = regex.Matches(File.ReadAllText(FILENAME));
this.OrderedKeys = new List<KeyValuePair<string, string>>();
this.Pairs = new Dictionary<string, KeyValuePair<string, string>>();
foreach (Match match in matches)
{
KeyValuePair<string, string> pair =
new KeyValuePair<string,string>(match.Groups["key"].Value, match.Groups["val"].Value);
this.OrderedKeys.Add(pair);
this.Pairs.Add(pair.Key, pair);
}
}
private void WriteFile()
{
if (File.Exists(FILENAME))
File.Delete(FILENAME);
using (System.IO.StreamWriter file = new System.IO.StreamWriter(FILENAME))
{
foreach (KeyValuePair<string, string> pair in this.OrderedKeys)
{
file.WriteLine(pair.Key + " = " + pair.Value);
}
}
}
}
Notice that the options object will read from the file once, and writeout when it is destroyed, meanwhile it will hold a local dictionary of the values in your file. You can then GetKey() and SetKey() to get and set your options.
I modified my original post to use a list and a dictionary, this is because a Dictionary on its own does not maintain the original order that pairs are added, so the list ensures that the options are always written to the file in the correct order.
You will also notice I threw in a Regular Expression to parse your file, makes things much easier and quicker and allows for things like extra whitespace in the options file.
Once you have done this it is easy to add functions like
public List<float> GetListFloatKey(string keybase)
{
List<float> ret = new List<float>();
foreach (string key in this.Pairs.Keys)
{
if (Regex.IsMatch(key, keybase + "[0-9]+"))
ret.Add(float.Parse(this.Pairs[key].Value));
}
return ret;
}
public void SetListFloatKey(string keybase, List<float> values)
{
List<string> oldkeys = new List<string>();
int startindex = -1;
foreach (string key in this.Pairs.Keys)
{
if (Regex.IsMatch(key, keybase + "[0-9]+"))
{
if (startindex == -1)
startindex = this.OrderedKeys.IndexOf(this.Pairs[key]);
oldkeys.Add(key);
}
}
foreach (string key in oldkeys)
{
this.OrderedKeys.Remove(this.Pairs[key]);
this.Pairs.Remove(key);
}
for (int i = 0; i < values.Count; i++)
{
KeyValuePair<string, string> pair = new KeyValuePair<string, string>(keybase + i.ToString(), values[i].ToString());
if (startindex != -1)
this.OrderedKeys.Insert(startindex + i, pair);
else
this.OrderedKeys.Add(pair);
this.Pairs.Add(pair.Key, pair);
}
}
It is easier to do that at this point because you have abstracted the actual file structure away and are now just dealing with a Dictionary

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.