I wrote a merge sort program, but I have problems calling It from another class. I need help. For some reason after I enter the size and the max number a get a black screen in the output. I believe that the solution is pretty easy, but I can't find the solution by myself
This is the class where It sorts the numbers
class MergeSort
{
public int[] Sort(int[] unsortedSequence)
{
int[] left;
int[] right;
int[] result = new int[unsortedSequence.Length];
if (unsortedSequence.Length <= 1)
return unsortedSequence;
int midPoint = unsortedSequence.Length / 2;
left = new int[midPoint];
if (unsortedSequence.Length % 2 == 0)
right = new int[midPoint];
else
right = new int[midPoint + 1];
for (int i = 0; i < midPoint; i++)
left[i] = unsortedSequence[i];
int x = 0;
for (int i = midPoint; i < unsortedSequence.Length; i++)
{
right[x] = unsortedSequence[i];
x++;
}
left = Sort(left);
right = Sort(right);
result = merge(left, right);
return result;
}
public static int[] merge(int[] left, int[] right)
{
int resultLength = right.Length + left.Length;
int[] result = new int[resultLength];
int indexLeft = 0, indexRight = 0, indexResult = 0;
while (indexLeft < left.Length || indexRight < right.Length)
{
if (indexLeft < left.Length && indexRight < right.Length)
{
if (left[indexLeft] <= right[indexRight])
{
result[indexResult] = left[indexLeft];
indexLeft++;
indexResult++;
}
else
{
result[indexResult] = right[indexRight];
indexRight++;
indexResult++;
}
}
else if (indexLeft < left.Length)
{
result[indexResult] = left[indexLeft];
indexLeft++;
indexResult++;
}
else if (indexRight < right.Length)
{
result[indexResult] = right[indexRight];
indexRight++;
indexResult++;
}
}
return result;
}
}
And this is the class where I'm trying to call the mergesort
class Program
{
static void Main(string[] args)
{
Console.Write("How Many Random Numbers Would you like to Generate : ");
int n = Convert.ToInt32(Console.ReadLine());
Console.Write("What is the Maximum Random Number Would you like to Generate : ");
int max = Convert.ToInt32(Console.ReadLine());
Console.Clear();
int[] unsortedSequence = generateRandomSequence(n, max);
MergeSort mergeSortEngine = new MergeSort();
int[] mergeSortedArray = mergeSortEngine.Sort(unsortedSequence);
Console.Write("Output for Merge Sort: \n\n");
OutputSequence(mergeSortedArray);
Console.WriteLine("\n\nPress Any Key to Continue...");
Console.ReadKey();
Console.Clear();
Because you didn't provide them, I wrote the missing generateRandomSequence() and OutputSequence methods in order to test your code and I can't reproduce your issue. Perhaps you should compare these to your own:
static int[] generateRandomSequence(int count, int max)
{
Random rn = new Random();
int[] seq = new int[count];
for (int i = 0; i < count; ++i)
{
seq[i] = rn.Next(0, max + 1);
}
return seq;
}
static void OutputSequence(int[] array)
{
for (int i = 0; i < array.Length; ++i)
{
if (i > 0)
{
Console.Write(", ");
}
Console.Write(array[i]);
}
Console.WriteLine();
}
Output from your code using the above methods:
It looks like you missing generateRandomSequence(n, max);
It might be like
public static int[] generateRandomSequence(int n, int max)
{
var rnd = new Random();
int[] seq = new int[n];
for (int ctr = 0; ctr < n; ctr++)
{
seq[ctr] = rnd.Next(1, max + 1);
}
return seq;
}
Then, in Program/Test class after Console.Write("Output for Merge Sort: \n\n"); you can iterate with foreach loop to display the sorted array.
foreach (var item in mergeSortedArray)
{
Console.WriteLine("{0}", item);
}
//OutputSequence(mergeSortedArray);
I implemented a recursive algorithm in C # that lists all possible combinations of N from K , it wroked very well, very reliable results, now I needed to implement it in java, I did , but the results are missing? many cases are not listed, after trying to see more than once where is the problem , I want you to try to see the problem with me. Thank you
C# Code :
static List<string> Combinations(List<string> motList, int Longeur)
{
List<String> Resultat = new List<string>();
for (int i = 0; i < motList.Count; i++)
{
if (Longeur == 1)
Resultat.Add(motList[i]);
else
{
List<string> ListIntermediaire = motList.GetRange(i + 1, motList.Count - (i + 1));
List<string> CombiList = Combinations(ListIntermediaire, Longeur - 1);
foreach (string s in CombiList)
Resultat.Add(motList[i] + s);
}
}
return Resultat;
}
Java code :
//function to get sub arrayList (getRange in c#)
public static ArrayList subArrayList (ArrayList ls , int i , int j)
{
ArrayList res = new ArrayList ();
for (int k = i; k <= j ; k++) {
res.add(ls.get(k));
}
return res;
}
//Java version of combination function
public static ArrayList Combinaison (ArrayList motList, int Longeur)
{
ArrayList Resultat = new ArrayList();
for (int i = 0; i <motList.size() ; i++) {
if (1 == Longeur )
Resultat.add(motList.get(i));
else
{
ArrayList ListIntermediaire = subArrayList(motList,i+1 , motList.size()-(i+1));
ArrayList CombiList = Combinaison(ListIntermediaire, Longeur-1);
for (int j = 0; j < CombiList.size(); j++)
Resultat.add( motList.get(i) +""+ CombiList.get(j) );
}
}
return Resultat;
}
Okay yes I see your point. Solution for combinations (and not permutations):
public static void main(final String[] args) {
ArrayList<String> list = new ArrayList<>();
list.add("1");
list.add("2");
list.add("3");
list.add("4");
list.add("5");
List<String> result = getCombinations(list, 2);
System.out.println(result.size());
System.out.println(result);
}
private static List<String> getCombinations(final List<String> list, final int length) {
if (length >= 1) {
return removeUntilLength(list, length, 0);
}
return new ArrayList<>();
}
private static List<String> removeUntilLength(final List<String> list, final int length, final int lastIdx) {
List<String> ret = new ArrayList<>();
if (list.size() == length) {
ret.add(list.toString());
} else {
for (int i = lastIdx; i < list.size(); i++) {
List<String> tmp = new ArrayList<>(list);
tmp.remove(i);
ret.addAll(removeUntilLength(tmp, length, Math.max(i, 0)));
}
}
return ret;
}
Your code is not very much adhering to Java coding standards, I mashed up another solution if this was any help:
public static void main(final String[] args) {
ArrayList<String> list = new ArrayList<>();
list.add("1");
list.add("2");
list.add("3");
list.add("4");
list.add("5");
List<String> result = getCombinations(list, 3);
System.out.println(result);
}
private static List<String> getCombinations(final List<String> list, final int length) {
List<String> ret = new ArrayList<>();
if (length >= 1) {
for (int j = 0; j < list.size(); j++) {
List<String> tmp = new ArrayList<>(list);
String excluded = tmp.remove(j);
List<String> remainingCombinations = getCombinations(tmp, length - 1);
if (remainingCombinations.size() > 0) {
for (String s : remainingCombinations) {
String combination = excluded + s;
ret.add(combination);
}
} else {
ret.add(excluded);
}
}
}
return ret;
}
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.