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How to convert ND array to 1D and revert it back

I need to convert n array (dimension is not known) to 1d and revert it back to nd array.
I loop through the whole array and add elements to 1d to convert, but I don't know how to revert it back.
public class ArrayND<T>
{
private int[] _lengths;
private Array _array;
public ArrayND(int[] length)
{
_lengths = length;
_array = Array.CreateInstance(typeof (T), _lengths);
}
}
///Loop through
public float[] ConvertTo1D(ArrayND<float> ndArray)
{
float[] OneDArray = new float[ndArray.Values.Length];
System.Collections.IEnumerator myEnumerator = ndArray.Values.GetEnumerator();
int cols = ndArray.Values.GetLength(ndArray.Values.Rank - 1);
int j = 0;
while (myEnumerator.MoveNext())
{
OneDArray[j] = (float)myEnumerator.Current;
j++;
}
return OneDArray;
}

public class ArrayND<T>
{
private int[] _lengths;
private Array _array;
public ArrayND(int[] length)
{
_lengths = length;
_array = Array.CreateInstance(typeof(T), _lengths);
}
public T GetValue(int[] index) => (T)_array.GetValue(index);
public void SetValue(T value, int[] index) => _array.SetValue(value, index);
public T[] ToOneD() => _array.Cast<T>().ToArray();
public static ArrayND<T> FromOneD(T[] array, int[] lengths)
{
if (array.Length != lengths.Aggregate((i, j) => i * j))
throw new ArgumentException("Number of elements in source and destination arrays does not match.");
var factors = lengths.Select((item, index) => lengths.Skip(index).Aggregate((i, j) => i * j)).ToArray();
var factorsHelper = factors.Zip(factors.Skip(1).Append(1), (Current, Next) => new { Current, Next }).ToArray();
var res = new ArrayND<T>(lengths);
for (var i = 0; i < array.Length; i++)
res.SetValue(array[i],
factorsHelper.Select(item => i % item.Current / item.Next).ToArray());
return res;
}
public override bool Equals(object obj) =>
(obj is ArrayND<T> ndArray) &&
_lengths.SequenceEqual(ndArray._lengths) &&
_array.Cast<T>().SequenceEqual(ndArray._array.Cast<T>());
public override int GetHashCode() =>
new[] { 17 }
.Concat(_lengths.Select(i => i.GetHashCode()))
.Concat(_array.Cast<T>().Select(i => i.GetHashCode()))
.Aggregate((i, j) => unchecked(23 * i + j));
}
It works with any number of dimensions.
Test it:
int I = 2, J = 3, K = 4;
var a = new ArrayND<int>(new[] { I, J, K });
var v = 0;
for (var i = 0; i < I; i++)
for (var j = 0; j < J; j++)
for (var k = 0; k < K; k++)
a.SetValue(++v, new[] { i, j, k });
var b = a.ToOneD();
var c = ArrayND<int>.FromOneD(b, new[] { I, J, K });
Console.WriteLine(a.Equals(c)); // True
or:
int I = 2, J = 3;
var a = new ArrayND<int>(new[] { I, J });
var v = 0;
for (var i = 0; i < I; i++)
for (var j = 0; j < J; j++)
a.SetValue(++v, new[] { i, j });
var b = a.ToOneD();
var c = ArrayND<int>.FromOneD(b, new[] { I, J });
Console.WriteLine(a.Equals(c)); // True
or:
int I = 2, J = 3, K = 4, M = 5;
var a = new ArrayND<int>(new[] { I, J, K, M });
var v = 0;
for (var i = 0; i < I; i++)
for (var j = 0; j < J; j++)
for (var k = 0; k < K; k++)
for (var m = 0; m < M; m++)
a.SetValue(++v, new[] { i, j, k, m });
var b = a.ToOneD();
var c = ArrayND<int>.FromOneD(b, new[] { I, J, K, M });
Console.WriteLine(a.Equals(c)); // True

Well, I solve it in a weird way. I am open to better approaches
public ArrayND<string> convert1DtoND(string[] oneDarray, int[] dimension)
{
ArrayND<string> ndArray = new ArrayND<string>(dimension);
int[] index = new int[ndArray.Values.Rank];
int[] length = new int[ndArray.Values.Rank];
int j = 0;
for (int i = 0; i < length.Length; i++)
{
length[i] = ndArray.Values.GetLength(i);
}
do
{
ndArray[index] = oneDarray[j];
j++;
} while (Increment(index, length));
return ndArray;
}
public static bool Increment(int[] index, int[] length)
{
int i = index.Length - 1;
index[i]++;
while (i >= 0 && index[i] == length[i] && length[i] > 0)
{
index[i--] = 0;
if (i >= 0)
index[i]++;
}
if (i < 0 || length[i] == 0)
return false;
else
return true;
}

How do i skip same values between 2 arrays

I'm stuck at "sorting" 2 different arrays.
My goal is to get rid of numbers that are included in array1 and array2.
Here is an example:
int [] arr1 = {1,2,3,4,5,6 } ;
int [] arr2 = {3,4} ;
Values in array arr1 should be like this : 1,2,5,6 (without 3 and 4)
My code so far:
static int[] test(int[]a,int[]b)
{
int i = 0;
int g = 0;
int d = 0;
int indexB = 0;
while( i < a.Length)
{
bool dvojnost = false;
int j = 0;
while (j<b.Length)
{
if (a[i] == b[j])
{
dvojnost = true;
indexB = j;
break;
}
else
j++;
}
int trenutniElementB = 0;
if(dvojnost==true)
{
while (trenutniElementB < b.Length)
{
if (trenutniElementB != indexB)
{
b[g] = b[trenutniElementB];
g++;
trenutniElementB++;
}
else
{
trenutniElementB++;
}
}
}
int h = 0;
if (dvojnost == true)
{
while (h < a.Length)
{
if (h != i)
{
a[d] = a[h];
d++;
h++;
}
else
{
h++;
}
}
}
i++;
}
return a;
}
This coding is only for extending my knowledge with arrays :)

Use LINQ :-)
int[] result = array1.Except(array2).ToArray();

If you are determined on using only loops and no Linq or Lists you could go for this...
static void Main(string[] args)
{
int[] arr1 = { 1, 2, 3, 4, 5, 6 };
int[] arr2 = { 3, 4 };
int[] result = test(arr1, arr2);
}
static int[] test(int[] a, int[] b)
{
int k = 0;
bool toAdd;
int[] output = new int[] { };
for (int i = 0; i < a.Length; i++)
{
toAdd = true;
for (int j = 0; j < b.Length; j++)
{
if (a[i] == b[j])
{
toAdd = false;
break;
}
}
if (toAdd)
{
Array.Resize(ref output, k + 1);
output[k] = a[i];
k++;
}
}
return output;
}

If you are treating second array as exclusion list for your result then maybe using generic List<> class will be enough to create simple code like this:
static int[] test(int[] a, int[] b)
{
List<int> result = new List<int>();
List<int> exclusion = new List<int>(b);
for (int i = 0; i < a.Length; i++)
{
if (exclusion.IndexOf(a[i]) >= 0)
continue;
result.Add(a[i]);
}
return result.ToArray();
}

Split your method into 2 parts.
First get rid of duplicates and then sort the array:
public int[] RemoveAndSort(int[] a, int[] b){
List<int> temp = new List<int>();
for(int i = 0; i < a.Length; i++){
bool found = false;
for(int j = 0; j < b.Length; j++){
if(a[i] == b[j]){
found = true;
}
}
if(!found) temp.Add(a[i]);
}
temp.Sort();
return temp.ToArray();
}
I used a List in my solution but you could also use a new empty array that is the same length of a at the start of the method.

Don't reinvent the wheel, use LINQ. Anyhow, if you are doing this as an excercise to understand arrays, here is an impementation that avoids LINQ altoghether:
public static T[] Except<T>(this T[] first, T[] second)
{
if (first == null)
throw new ArgumentNullException(nameof(first));
if (second == null)
throw new ArgumentNullException(nameof(second));
if (second.Length == 0)
return first;
var counter = 0;
var newArray = new T[first.Length];
foreach (var f in first)
{
var found = false;
foreach (var s in second)
{
if (f.Equals(s))
{
found = true;
break;
}
}
if (!found)
{
newArray[counter] = f;
counter++;
}
}
Array.Resize(ref newArray, counter);
return newArray;
}

You can try this, without any generics collections :) Only arrays:
public class Program
{
static void Main(string[] args)
{
int resultLength = 0;
int[] arr1 = { 1, 2, 3, 4, 5, 6 };
int[] arr2 = { 3, 4 };
int[] result = new int[resultLength];
for(int i = 0; i < arr1.Length; i++)
{
if(!arr2.Exists(arr1[i]))
{
resultLength++;
Array.Resize(ref result, resultLength);
result[resultLength- 1] = arr1[i];
}
}
}
}
public static class MyExtensions
{
public static bool Exists(this int[] array, int value)
{
for(int i = 0; i < array.Length; i++)
{
if (array[i] == value)
return true;
}
return false;
}
}

How to find possible set of k Elements from array?

I have an array {1,2,3,4,5,6,7,8,9,10} and I have to find all combinations of k elements from array and k will be dynamic. So for 4 elements below code is sufficient but i have to make this dynamic means,it is not fixed that how many for loops will be used, so please suggest some solution for this.
for (i = 0; i < len - 3; i++)
{
for (j = i + 1; j < len - 2; j++)
{
for (y = j + 1; y < len - 1; y++)
{
for (k = y + 1; k < len; k++)
Console.WriteLine("{0},{1},{2},{3}", s[i], s[j],s[y], s[k]);
}
}
}

All you need is to replace i, j, y, ... with array and manually unroll the for loops like this
static void PrintCombinations(int[] input, int k)
{
var indices = new int[k];
for (int pos = 0, index = 0; ; index++)
{
if (index <= input.Length - k + pos)
{
indices[pos++] = index;
if (pos < k) continue;
// Consume the combination
for (int i = 0; i < k; i++)
{
if (i > 0) Console.Write(",");
Console.Write(input[indices[i]]);
}
Console.WriteLine();
pos--;
}
else
{
if (pos == 0) break;
index = indices[--pos];
}
}
}

You can use this methods for generating combinations of size l
public static List<List<T>> GenerateCombinations<T>(List<T> items, int l)
{
if (l == 0)
return new List<List<T>> { new List<T>() };
var allCombs = new List<List<T>>();
for (int i = 0; i < items.Count(); i++)
{
var listWithRemovedElement = new List<T>(items);
listWithRemovedElement.RemoveRange(0, i + 1);
foreach (var combination in GenerateCombinations(listWithRemovedElement, l - 1))
{
var comb = new List<T>(listWithRemovedElement.Count + 1);
comb.Add(items[i]);
comb.AddRange(combination);
allCombs.Add(comb);
}
}
return allCombs;
}
You can use this methods for generating permutations of size l
public static List<List<T>> GeneratePermutations<T>(List<T> items, int l)
{
if (l == 0)
return new List<List<T>> { new List<T>() };
var allCombs = new List<List<T>>();
for (int i = 0; i < items.Count(); i++)
{
var listWithRemovedElement = new List<T>(items);
listWithRemovedElement.RemoveAt(i);
foreach (var combination in GeneratePermutations(listWithRemovedElement, l - 1))
{
var comb = new List<T>(listWithRemovedElement.Count + 1);
comb.Add(items[i]);
comb.AddRange(combination);
allCombs.Add(comb);
}
}
return allCombs;
}
Permutationsof { 1, 2, 3 } with size of 2
var result = GeneratePermutations(new List<int>() { 1, 2, 3 }, 2);
foreach (var perm in result)
Console.WriteLine(string.Join(",", perm));
1,2
1,3
2,1
2,3
3,1
3,2
Combinations of { 1, 2, 3 } with size of 2
var result = GenerateCombinations(new List<int>() { 1, 2, 3 }, 2);
foreach (var comb in result)
Console.WriteLine(string.Join(",", comb));
1,2
1,3
2,3

This isn't how I'd do it in "real life", but since this seems to be a simple homework-style problem aimed at getting you to use recursion and with the aim of simply writing out the combinations, this is a reasonably simple solution:
class Program
{
public static void Main()
{
int[] test = { 1, 2, 3, 4, 5 };
int k = 4;
WriteCombinations(test, k);
Console.ReadLine();
}
static void WriteCombinations(int[] array, int k, int startPos = 0, string prefix = "")
{
for (int i = startPos; i < array.Length - k + 1; i++)
{
if (k == 1)
{
Console.WriteLine("{0}, {1}", prefix, array[i]);
}
else
{
string newPrefix = array[i].ToString();
if (prefix != "")
{
newPrefix = string.Format("{0}, {1}", prefix, newPrefix);
}
WriteCombinations(array, k - 1, i + 1, newPrefix);
}
}
}
}
If having optional parameters is not "basic" enough, then you can either take away the default values and pass in 0 and "" on the first call, or you can create another "wrapper" method that takes fewer parameters and then calls the first method with the defaults.

Combining two double[] arrays into double[,]

I frequently have two arrays that I need to combine to one matrix (same lenght and type). I was wondering whether there is a linq way that is more elegant than:
var result = new double[dt.Count, 2];
for (int i = 0; i < dt.Count; i++)
{
result[i, 0] = dts[i];
result[i, 1] = dt[i];
}
I tried
var result = dts.zip(dt, (a,b) => new{a,b})
and:
var result = dts.Concat(dt).ToArray()
But neither do what I would like to do...

There is nothing in the framework, but here is a general solution (that works for 2 or more arrays):
public static class ArrayConvert
{
public static T[,] To2DArray<T>(params T[][] arrays)
{
if (arrays == null) throw new ArgumentNullException("arrays");
foreach (var a in arrays)
{
if (a == null) throw new ArgumentException("can not contain null arrays");
if (a.Length != arrays[0].Length) throw new ArgumentException("input arrays should have the same length");
}
var height = arrays.Length;
var width = arrays[0].Length;
var result = new T[width, height];
for (int i = 0; i < height; i++)
for (int j = 0; j < width; j++)
{
result[i, j] = arrays[i][j];
}
return result;
}
}
Which can then be used as follows:
var convertedArray = ArrayConvert.To2DArray(new[]{1,2,3}, new[]{4,5,6}, new[]{7,8,9});

ok then use this
class Program {
static void Main(string[] args) {
double[,] x = { { 1, 2, 3 }, { 4, 5, 6 } };
double[,] y = { { 7, 8, 9 }, { 10, 11, 12 } };
var xy = new StitchMatrix<int>(x, y);
Console.WriteLine("0,0=" + xy[0, 0]); // 1
Console.WriteLine("1,1=" + xy[1, 1]); // 5
Console.WriteLine("1,2=" + xy[1, 2]); // 6
Console.WriteLine("2,2=" + xy[2, 2]); // 9
Console.WriteLine("3,2=" + xy[3, 2]); // 12
}
}
class StitchMatrix<T> {
private T[][,] _matrices;
private double[] _lengths;
public StitchMatrix(params T[][,] matrices) {
// TODO: check they're all same size
_matrices = matrices;
// call uperbound once for speed
_lengths = _matrices.Select(m => m.GetUpperBound(0)).ToArray();
}
public T this[double x, double y] {
get {
// find the right matrix
double iMatrix = 0;
while (_lengths[iMatrix] < x) {
x -= (_lengths[iMatrix] + 1);
iMatrix++;
}
// return value at cell
return _matrices[iMatrix][x, y];
}
}
}

Here is another solution. I "prepare" the input for LINQ processing. Don't sure that this is elegant, but it is LINQ:
// the input
double[] dts = { 1, 2, 3, 4, 5 };
double[] dt = { 10, 20, 30, 40, 50 };
// list of lists, for iterating the input with LINQ
double[][] combined = { dts, dt };
var indexes = Enumerable.Range(0, dt.Length);
var subIndexes = Enumerable.Range(0, 2);
// the output
var result = new double[dt.Length, 2];
var sss = from i in indexes
from j in subIndexes
select result[i, j] = combined[j][i];
// just to activate the LINQ iterator
sss.ToList();

I suggest against doing it directly in LINQ. You can write a generic method to do it for you, something like:
public static T[,] To2DArray<T>(this T[][] arr)
{
if (arr.Length == 0)
{
return new T[,]{};
}
int standardLength = arr[0].Length;
foreach (var x in arr)
{
if (x.Length != standardLength)
{
throw new ArgumentException("Arrays must have all the same length");
}
}
T[,] solution = new T[arr.Length, standardLength];
for (int i = 0; i < arr.Length; i++)
{
for (int j = 0; j < standardLength; j++)
{
solution[i, j] = arr[i][j];
}
}
return solution;
}

I know that wasnt the question but the most elegant answer is to use f#:
let combinearrays (arr1:array<'a>) (arr2:array<'a>) =
let rws = arr1|> Array.length
Array2D.init rws 2 (fun i j -> match j with |0 -> arr1.[i] |1 -> arr2.[i])
From John see here

Here is the solution Convert two 1d Arrays in one 2D Array which I developed for my own use.
(from a1 in array1.Select((n,index)=>new{Index=index,c1=n}).ToList()
join a2 in array2.Select((n,index)=>new {Index=index,c2=n}).ToList() on a1.Index equals a2.Index
select new {c1,c2}
).ToArray()

How do I remove duplicates from a C# array?

I have been working with a string[] array in C# that gets returned from a function call. I could possibly cast to a Generic collection, but I was wondering if there was a better way to do it, possibly by using a temp array.
What is the best way to remove duplicates from a C# array?

You could possibly use a LINQ query to do this:
int[] s = { 1, 2, 3, 3, 4};
int[] q = s.Distinct().ToArray();

Here is the HashSet<string> approach:
public static string[] RemoveDuplicates(string[] s)
{
HashSet<string> set = new HashSet<string>(s);
string[] result = new string[set.Count];
set.CopyTo(result);
return result;
}
Unfortunately this solution also requires .NET framework 3.5 or later as HashSet was not added until that version. You could also use array.Distinct(), which is a feature of LINQ.

The following tested and working code will remove duplicates from an array. You must include the System.Collections namespace.
string[] sArray = {"a", "b", "b", "c", "c", "d", "e", "f", "f"};
var sList = new ArrayList();
for (int i = 0; i < sArray.Length; i++) {
if (sList.Contains(sArray[i]) == false) {
sList.Add(sArray[i]);
}
}
var sNew = sList.ToArray();
for (int i = 0; i < sNew.Length; i++) {
Console.Write(sNew[i]);
}
You could wrap this up into a function if you wanted to.

If you needed to sort it, then you could implement a sort that also removes duplicates.
Kills two birds with one stone, then.

This might depend on how much you want to engineer the solution - if the array is never going to be that big and you don't care about sorting the list you might want to try something similar to the following:
public string[] RemoveDuplicates(string[] myList) {
System.Collections.ArrayList newList = new System.Collections.ArrayList();
foreach (string str in myList)
if (!newList.Contains(str))
newList.Add(str);
return (string[])newList.ToArray(typeof(string));
}

List<String> myStringList = new List<string>();
foreach (string s in myStringArray)
{
if (!myStringList.Contains(s))
{
myStringList.Add(s);
}
}
This is O(n^2), which won't matter for a short list which is going to be stuffed into a combo, but could be rapidly be a problem on a big collection.

-- This is Interview Question asked every time. Now i done its coding.
static void Main(string[] args)
{
int[] array = new int[] { 4, 8, 4, 1, 1, 4, 8 };
int numDups = 0, prevIndex = 0;
for (int i = 0; i < array.Length; i++)
{
bool foundDup = false;
for (int j = 0; j < i; j++)
{
if (array[i] == array[j])
{
foundDup = true;
numDups++; // Increment means Count for Duplicate found in array.
break;
}
}
if (foundDup == false)
{
array[prevIndex] = array[i];
prevIndex++;
}
}
// Just Duplicate records replce by zero.
for (int k = 1; k <= numDups; k++)
{
array[array.Length - k] = '\0';
}
Console.WriteLine("Console program for Remove duplicates from array.");
Console.Read();
}

Here is a O(n*n) approach that uses O(1) space.
void removeDuplicates(char* strIn)
{
int numDups = 0, prevIndex = 0;
if(NULL != strIn && *strIn != '\0')
{
int len = strlen(strIn);
for(int i = 0; i < len; i++)
{
bool foundDup = false;
for(int j = 0; j < i; j++)
{
if(strIn[j] == strIn[i])
{
foundDup = true;
numDups++;
break;
}
}
if(foundDup == false)
{
strIn[prevIndex] = strIn[i];
prevIndex++;
}
}
strIn[len-numDups] = '\0';
}
}
The hash/linq approaches above are what you would generally use in real life. However in interviews they usually want to put some constraints e.g. constant space which rules out hash or no internal api - which rules out using LINQ.

protected void Page_Load(object sender, EventArgs e)
{
string a = "a;b;c;d;e;v";
string[] b = a.Split(';');
string[] c = b.Distinct().ToArray();
if (b.Length != c.Length)
{
for (int i = 0; i < b.Length; i++)
{
try
{
if (b[i].ToString() != c[i].ToString())
{
Response.Write("Found duplicate " + b[i].ToString());
return;
}
}
catch (Exception ex)
{
Response.Write("Found duplicate " + b[i].ToString());
return;
}
}
}
else
{
Response.Write("No duplicate ");
}
}

Add all the strings to a dictionary and get the Keys property afterwards. This will produce each unique string, but not necessarily in the same order your original input had them in.
If you require the end result to have the same order as the original input, when you consider the first occurance of each string, use the following algorithm instead:
Have a list (final output) and a dictionary (to check for duplicates)
For each string in the input, check if it exists in the dictionary already
If not, add it both to the dictionary and to the list
At the end, the list contains the first occurance of each unique string.
Make sure you consider things like culture and such when constructing your dictionary, to make sure you handle duplicates with accented letters correctly.

The following piece of code attempts to remove duplicates from an ArrayList though this is not an optimal solution. I was asked this question during an interview to remove duplicates through recursion, and without using a second/temp arraylist:
private void RemoveDuplicate()
{
ArrayList dataArray = new ArrayList(5);
dataArray.Add("1");
dataArray.Add("1");
dataArray.Add("6");
dataArray.Add("6");
dataArray.Add("6");
dataArray.Add("3");
dataArray.Add("6");
dataArray.Add("4");
dataArray.Add("5");
dataArray.Add("4");
dataArray.Add("1");
dataArray.Sort();
GetDistinctArrayList(dataArray, 0);
}
private void GetDistinctArrayList(ArrayList arr, int idx)
{
int count = 0;
if (idx >= arr.Count) return;
string val = arr[idx].ToString();
foreach (String s in arr)
{
if (s.Equals(arr[idx]))
{
count++;
}
}
if (count > 1)
{
arr.Remove(val);
GetDistinctArrayList(arr, idx);
}
else
{
idx += 1;
GetDistinctArrayList(arr, idx);
}
}

Simple solution:
using System.Linq;
...
public static int[] Distinct(int[] handles)
{
return handles.ToList().Distinct().ToArray();
}

Maybe hashset which do not store duplicate elements and silently ignore requests to add
duplicates.
static void Main()
{
string textWithDuplicates = "aaabbcccggg";
Console.WriteLine(textWithDuplicates.Count());
var letters = new HashSet<char>(textWithDuplicates);
Console.WriteLine(letters.Count());
foreach (char c in letters) Console.Write(c);
Console.WriteLine("");
int[] array = new int[] { 12, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2 };
Console.WriteLine(array.Count());
var distinctArray = new HashSet<int>(array);
Console.WriteLine(distinctArray.Count());
foreach (int i in distinctArray) Console.Write(i + ",");
}

NOTE : NOT tested!
string[] test(string[] myStringArray)
{
List<String> myStringList = new List<string>();
foreach (string s in myStringArray)
{
if (!myStringList.Contains(s))
{
myStringList.Add(s);
}
}
return myStringList.ToString();
}
Might do what you need...
EDIT Argh!!! beaten to it by rob by under a minute!

Tested the below & it works. What's cool is that it does a culture sensitive search too
class RemoveDuplicatesInString
{
public static String RemoveDups(String origString)
{
String outString = null;
int readIndex = 0;
CompareInfo ci = CultureInfo.CurrentCulture.CompareInfo;
if(String.IsNullOrEmpty(origString))
{
return outString;
}
foreach (var ch in origString)
{
if (readIndex == 0)
{
outString = String.Concat(ch);
readIndex++;
continue;
}
if (ci.IndexOf(origString, ch.ToString().ToLower(), 0, readIndex) == -1)
{
//Unique char as this char wasn't found earlier.
outString = String.Concat(outString, ch);
}
readIndex++;
}
return outString;
}
static void Main(string[] args)
{
String inputString = "aAbcefc";
String outputString;
outputString = RemoveDups(inputString);
Console.WriteLine(outputString);
}
}
--AptSenSDET

This code 100% remove duplicate values from an array[as I used a[i]].....You can convert it in any OO language..... :)
for(int i=0;i<size;i++)
{
for(int j=i+1;j<size;j++)
{
if(a[i] == a[j])
{
for(int k=j;k<size;k++)
{
a[k]=a[k+1];
}
j--;
size--;
}
}
}

Generic Extension method :
public static IEnumerable<TSource> Distinct<TSource>(this IEnumerable<TSource> source, IEqualityComparer<TSource> comparer)
{
if (source == null)
throw new ArgumentNullException(nameof(source));
HashSet<TSource> set = new HashSet<TSource>(comparer);
foreach (TSource item in source)
{
if (set.Add(item))
{
yield return item;
}
}
}

you can using This code when work with an ArrayList
ArrayList arrayList;
//Add some Members :)
arrayList.Add("ali");
arrayList.Add("hadi");
arrayList.Add("ali");
//Remove duplicates from array
for (int i = 0; i < arrayList.Count; i++)
{
for (int j = i + 1; j < arrayList.Count ; j++)
if (arrayList[i].ToString() == arrayList[j].ToString())
arrayList.Remove(arrayList[j]);

Below is an simple logic in java you traverse elements of array twice and if you see any same element you assign zero to it plus you don't touch the index of element you are comparing.
import java.util.*;
class removeDuplicate{
int [] y ;
public removeDuplicate(int[] array){
y=array;
for(int b=0;b<y.length;b++){
int temp = y[b];
for(int v=0;v<y.length;v++){
if( b!=v && temp==y[v]){
y[v]=0;
}
}
}
}

public static int RemoveDuplicates(ref int[] array)
{
int size = array.Length;
// if 0 or 1, return 0 or 1:
if (size < 2) {
return size;
}
int current = 0;
for (int candidate = 1; candidate < size; ++candidate) {
if (array[current] != array[candidate]) {
array[++current] = array[candidate];
}
}
// index to count conversion:
return ++current;
}

The best way? Hard to say, the HashSet approach looks fast,
but (depending on the data) using a sort algorithm (CountSort ?)
can be much faster.
using System;
using System.Collections.Generic;
using System.Linq;
class Program
{
static void Main()
{
Random r = new Random(0); int[] a, b = new int[1000000];
for (int i = b.Length - 1; i >= 0; i--) b[i] = r.Next(b.Length);
a = new int[b.Length]; Array.Copy(b, a, b.Length);
a = dedup0(a); Console.WriteLine(a.Length);
a = new int[b.Length]; Array.Copy(b, a, b.Length);
var w = System.Diagnostics.Stopwatch.StartNew();
a = dedup0(a); Console.WriteLine(w.Elapsed); Console.Read();
}
static int[] dedup0(int[] a) // 48 ms
{
return new HashSet<int>(a).ToArray();
}
static int[] dedup1(int[] a) // 68 ms
{
Array.Sort(a); int i = 0, j = 1, k = a.Length; if (k < 2) return a;
while (j < k) if (a[i] == a[j]) j++; else a[++i] = a[j++];
Array.Resize(ref a, i + 1); return a;
}
static int[] dedup2(int[] a) // 8 ms
{
var b = new byte[a.Length]; int c = 0;
for (int i = 0; i < a.Length; i++)
if (b[a[i]] == 0) { b[a[i]] = 1; c++; }
a = new int[c];
for (int j = 0, i = 0; i < b.Length; i++) if (b[i] > 0) a[j++] = i;
return a;
}
}
Almost branch free. How? Debug mode, Step Into (F11) with a small array: {1,3,1,1,0}
static int[] dedupf(int[] a) // 4 ms
{
if (a.Length < 2) return a;
var b = new byte[a.Length]; int c = 0, bi, ai, i, j;
for (i = 0; i < a.Length; i++)
{ ai = a[i]; bi = 1 ^ b[ai]; b[ai] |= (byte)bi; c += bi; }
a = new int[c]; i = 0; while (b[i] == 0) i++; a[0] = i++;
for (j = 0; i < b.Length; i++) a[j += bi = b[i]] += bi * i; return a;
}
A solution with two nested loops might take some time,
especially for larger arrays.
static int[] dedup(int[] a)
{
int i, j, k = a.Length - 1;
for (i = 0; i < k; i++)
for (j = i + 1; j <= k; j++) if (a[i] == a[j]) a[j--] = a[k--];
Array.Resize(ref a, k + 1); return a;
}

private static string[] distinct(string[] inputArray)
{
bool alreadyExists;
string[] outputArray = new string[] {};
for (int i = 0; i < inputArray.Length; i++)
{
alreadyExists = false;
for (int j = 0; j < outputArray.Length; j++)
{
if (inputArray[i] == outputArray[j])
alreadyExists = true;
}
if (alreadyExists==false)
{
Array.Resize<string>(ref outputArray, outputArray.Length + 1);
outputArray[outputArray.Length-1] = inputArray[i];
}
}
return outputArray;
}

int size = a.Length;
for (int i = 0; i < size; i++)
{
for (int j = i + 1; j < size; j++)
{
if (a[i] == a[j])
{
for (int k = j; k < size; k++)
{
if (k != size - 1)
{
int temp = a[k];
a[k] = a[k + 1];
a[k + 1] = temp;
}
}
j--;
size--;
}
}
}

So I was doing an interview session and got the same question to sort and distinct
static void Sort()
{
try
{
int[] number = new int[Convert.ToInt32(Console.ReadLine())];
for (int i = 0; i < number.Length; i++)
{
number[i] = Convert.ToInt32(Console.ReadLine());
}
Array.Sort(number);
int[] num = number.Distinct().ToArray();
for (int i = 0; i < num.Length; i++)
{
Console.WriteLine(num[i]);
}
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
Console.Read();
}

using System;
using System.Collections.Generic;
using System.Linq;
namespace Rextester
{
public class Program
{
public static void Main(string[] args)
{
List<int> listofint1 = new List<int> { 4, 8, 4, 1, 1, 4, 8 };
List<int> updatedlist= removeduplicate(listofint1);
foreach(int num in updatedlist)
Console.WriteLine(num);
}
public static List<int> removeduplicate(List<int> listofint)
{
List<int> listofintwithoutduplicate= new List<int>();
foreach(var num in listofint)
{
if(!listofintwithoutduplicate.Any(p=>p==num))
{
listofintwithoutduplicate.Add(num);
}
}
return listofintwithoutduplicate;
}
}
}

strINvalues = "1,1,2,2,3,3,4,4";
strINvalues = string.Join(",", strINvalues .Split(',').Distinct().ToArray());
Debug.Writeline(strINvalues);
Kkk Not sure if this is witchcraft or just beautiful code
1 strINvalues .Split(',').Distinct().ToArray()
2 string.Join(",", XXX);
1 Splitting the array and using Distinct [LINQ] to remove duplicates
2 Joining it back without the duplicates.
Sorry I never read the text on StackOverFlow just the code. it make more sense than the text ;)

Removing duplicate and ignore case sensitive using Distinct & StringComparer.InvariantCultureIgnoreCase
string[] array = new string[] { "A", "a", "b", "B", "a", "C", "c", "C", "A", "1" };
var r = array.Distinct(StringComparer.InvariantCultureIgnoreCase).ToList();
Console.WriteLine(r.Count); // return 4 items

Find answer below.
class Program
{
static void Main(string[] args)
{
var nums = new int[] { 1, 4, 3, 3, 3, 5, 5, 7, 7, 7, 7, 9, 9, 9 };
var result = removeDuplicates(nums);
foreach (var item in result)
{
Console.WriteLine(item);
}
}
static int[] removeDuplicates(int[] nums)
{
nums = nums.ToList().OrderBy(c => c).ToArray();
int j = 1;
int i = 0;
int stop = 0;
while (j < nums.Length)
{
if (nums[i] != nums[j])
{
nums[i + 1] = nums[j];
stop = i + 2;
i++;
}
j++;
}
nums = nums.Take(stop).ToArray();
return nums;
}
}
Just a bit of contribution based on a test i just solved, maybe helpful and open to improvement by other top contributors here.
Here are the things i did:
I used OrderBy which allows me order or sort the items from smallest to the highest using LINQ
I then convert it to back to an array and then re-assign it back to the primary datasource
So i then initialize j which is my right hand side of the array to be 1 and i which is my left hand side of the array to be 0, i also initialize where i would i to stop to be 0.
I used a while loop to increment through the array by going from one position to the other left to right, for each increment the stop position is the current value of i + 2 which i will use later to truncate the duplicates from the array.
I then increment by moving from left to right from the if statement and from right to right outside of the if statement until i iterate through the entire values of the array.
I then pick from the first element to the stop position which becomes the last i index plus 2. that way i am able to remove all the duplicate items from the int array. which is then reassigned.