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;
}
}
I implemented MergeSort algorithm that's used on a 100,000 integer file. It takes care of the sorting and collects inversions that are in the file. It works with small test arrays, but as soon as I plug in the actual file, I get out of memory error. How do I fix it?
The error occurs during MergeSort, and the number of elements in my aux array is 12,500
Here's my code:
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Assignment_1
{
class Program
{
static void Main(string[] args)
{
List<int> data = File2Array("IntegerArray.txt");
int[] unsorted = data.ToArray();
List<string> inversions = new List<string>();
Sort(ref unsorted, ref inversions);
Console.WriteLine("number of inversions is: " + inversions.Count());
Console.ReadLine();
}
public static void Sort(ref int[] unsorted, ref List<string>inversions)
{
int size = unsorted.Length;
if (size == 1)
return;
int mid = size / 2;
int leftSize = mid;
int rightSize = size - leftSize;
int[] left = new int[leftSize];
int[] right = new int[rightSize];
Array.Copy(unsorted, 0, left, 0, leftSize);
Array.Copy(unsorted, mid, right, 0, rightSize);
Sort(ref left, ref inversions);
Sort(ref right, ref inversions);
int[] aux = new int[leftSize + rightSize];
for (int i = 0, j = 0, k = 0; k < aux.Length; k++)
{
if (left[i] < right[j])
{
aux[k] = left[i++];
// if left array is exhausted, copy the remaining right array elements over
if (i == leftSize)
{
Array.Copy(right, j, aux, ++k, rightSize - j);
unsorted = aux;
break;
}
}
else
{
int temp = i;
while (temp < leftSize)
{
inversions.Add(left[temp++] + "-" + right[j]);
}
aux[k] = right[j++];
if (j == rightSize)
{
Array.Copy(left, i, aux, ++k, leftSize - i);
unsorted = aux;
break;
}
}
}
}
public static List<int> File2Array(string file)
{
List<int> data = new List<int>();
using (StreamReader reader = new StreamReader(file))
{
int line;
do
{
int.TryParse(reader.ReadLine(), out line);
data.Add(line);
}
while (!reader.EndOfStream);
}
return data;
}
}
}
Here's some code for you to look at.
This starts with recognizing that the file is already a collection of single elements. Therefore we can do the first grouping/sorting when we read the file. Since arrays are very impractical for this part I used Lists and then cast the return to int[][]
static int[][] makearrays(string filename)
{
List<List<int>> outval = new List<List<int>>();
using(StreamReader sr = new StreamReader(filename))
{
while(!sr.EndOfStream)
{
int a = 0, b = 0;
a = int.Parse(sr.ReadLine());
if(!sr.EndOfStream)
b = int.Parse(sr.ReadLine());
else
{
outval.Add(new List<int>() { a });
break;
}
if(a > b)
outval.Add(new List<int>() { b, a });
else
outval.Add(new List<int>() { a, b });
}
}
return outval.Select(x => x.ToArray()).ToArray();
}
With this array we can start the rest of the grouping/sorting
This uses recursion but has a minimal memory footprint:
static int[][] dosort(int[][] input)
{
if(input.Length == 1)
return input;
int i = 1, m = 0;
for(; i < input.Length; i += 2)
{
int limit = Math.Min(input[i].Length, input[i - 1].Length);
int[] temp = new int[input[i].Length + input[i - 1].Length];
int j = 0, k = 0, l = 0;
while(j < input[i].Length && k < input[i - 1].Length)
{
if(input[i][j] < input[i - 1][k])
{
temp[l++] = input[i][j++];
}
else
temp[l++] = input[i - 1][k++];
}
while(l < temp.Length)
{
if(j < input[i].Length)
temp[l++] = input[i][j++];
if(k < input[i - 1].Length)
temp[l++] = input[i - 1][k++];
}
input[m++] = temp;
}
if(input.Length % 2 == 1)
input[m++] = input.Last();
input = input.Take(m).ToArray();
return dosort(input);
}
In my tests the 100000 element file was sorted in less than a quarter of a second, including reading it into memory.
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.