I am trying to implement a step counter into my bubble sort algorithm, but I don't know how to display the counter at the end of the sorting algorithm. If anyone could explain how I should go about this that would be great. Thank You.
My current code: (Bubble Sort):
static int[] bubbleSort(int[] arr, int n)
{
int stepCount = 0; // <- Counter to return and display
for (int i = 0; i < n - 1; i++)
{
for (int j = 0; j < n - 1 - i; j++)
{
if (arr[j + 1] < arr[j])
{
int temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
}
stepCount++;
}
}
return arr;
}
public static void DisplayArrayBubble(int[] arr)
{
foreach (int i in arr)
{
Console.Write(i.ToString() + " ");
}
}
Why not just return int - number of steps? I.e.
// arr : will be sorted
// return : number of steps
static int bubbleSort(int[] arr) {
if (null == arr)
return 0;
int stepCount = 0;
for (int i = 0; i < arr.Length - 1; i++)
for (int j = 0; j < arr.Length - 1 - i; j++)
if (arr[j + 1] < arr[j]) {
int temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
stepCount += 1;
}
return stepCount;
}
Demo:
int[] sample = new int[] {1, 5, 4, 3, 2, 7};
int steps = bubbleSort(sample);
Console.WriteLine($"Sorted [{string.Join(", ", sample)}] in {steps} steps");
Outcome:
Sorted [1, 2, 3, 4, 5, 7] in 6 steps
There a plethora of ways but one is to make a custom class to hold both pieces of information that you need:
public class BubbleObject
{
public int[] arr { get; set; }
public int stepCount { get; set; }
}
Then adjust the code you have to use that object:
static BubbleObject bubbleSort(int[] arr, int n)
{
int stepCount = 0;
for (int i = 0; i < n - 1; i++)
{
for (int j = 0; j < n - 1 - i; j++)
{
if (arr[j + 1] < arr[j])
{
int temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
}
stepCount++;
}
}
BubbleObject bo = new BubbleObject() { arr=arr, stepCount=stepCount}
return bo;
}
public static void DisplayArrayBubble(BubbleObject bo)
{
Console.WriteLine("Number of Steps = " + bo.stepCount);
foreach (int i in bo.arr)
{
Console.Write(i.ToString() + " ");
}
}
That should do it. There are other ways as well.
I've read the CLRS and tried to implement the recursive merge sort algorithm . cant see what the error is but everytime i run it gives me an "Index out of bounds error "
i've been trying for 5h now
static public void MergeSort(int[] input, int IndexStanga, int IndexDreapta)
{
if (IndexStanga < IndexDreapta)
{
int IndexMijloc = (IndexDreapta + IndexStanga) / 2;
MergeSort(input, IndexStanga, IndexMijloc);
MergeSort(input, IndexMijloc + 1, IndexDreapta);
Merge(input, IndexStanga, IndexDreapta, IndexMijloc);
}
}
static public void Merge(int[] input, int stanga, int dreapta, int mijloc)
{
int lungDR = 0;
int lunST = 0;
lungDR = dreapta - mijloc;
lunST = mijloc - stanga + 1;
int[] valDreapta = new int[lungDR + 1];
int[] valStanga = new int[lunST + 1];
valDreapta[valDreapta.Length - 1] = int.MaxValue;
valStanga[valStanga.Length - 1] = int.MaxValue;
int i = 0;
int j = 0;
for (i = stanga; i <= mijloc; i++) valStanga[i] = input[i];
for (i = 0; i < lungDR; i++) { valDreapta[i] = input[i + mijloc + 1]; }
i = 0;
j = 0;
for (int k = 0; k < input.Length; k++)
{
if (valStanga[i] <= valDreapta[j]) //error out of bounds
{
input[k] = valStanga[i];
i++;
}
else
{
input[k] = valDreapta[j];
j++;
}
}
}
Fixes noted in comments below. First fix for moving data from input to valStanga. Second fix for the range on merging back to input. The parameters for merge are in an unusual order, first, last, middle. Normally the order is first, middle, last.
Comments: The program will have issues if the array to be sorted contains elements equal to max integer. It would be more efficient to do a one time allocation of a working array, rather than allocate new sub-arrays on every call to merge. The copy operations can be avoided by changing the direction of merge with each level of recursion.
int i = 0;
int j = 0;
for (i = 0; i < lungDR; i++) { valDreapta[i] = input[i + mijloc + 1]; }
for (i = 0; i < lunST; i++) { valStanga[i] = input[i + stanga]; } // fix
i = 0;
j = 0;
for (int k = stanga; k <= dreapta; k++) // fix
{
if (valStanga[i] <= valDreapta[j])
I am trying to calculate a 3D linear regression LINE using the Singular Value Decomposition method (SVD).
This works fine. Now, I'd like to generalise the method for weighted regression.
how to calculate the optimale beta with SVD? Below is my C# code which uses the CSML package. The LinearRegression() function works just fine. WeightedLinearRegression() does not and I assume this is because I cannot just simply define
weighted_mult_mat = M_tr * W * M;
CODE:
public static Vector3D WeightedLinearRegression(List<Point3D> pts, List<double> weights) {
// normalisation
double sum = weights.Sum();
if (sum != weights.Count) {
for (int i = 0; i < weights.Count; i++ ) {
weights[i] = weights[i] / sum;
}
}
Point3D avg = pts.average();
// populate Matrix M
CSML.Matrix M = new CSML.Matrix(pts.Count, 3); // init
// populate matrix M
for (int i = 1; i < pts.Count + 1; i++) {
M[i, 1] = new Complex(pts[i - 1].X - avg.X);
M[i, 2] = new Complex(pts[i - 1].Y - avg.Y);
M[i, 3] = new Complex(pts[i - 1].Z - avg.Z);
}
CSML.Matrix M_tr = M.Transpose();
// populate weights matrix
CSML.Matrix W = new CSML.Matrix(pts.Count, pts.Count); // init
for (int i = 1; i < pts.Count + 1; i++) {
W[i, i] = new Complex(weights[i-1]);
}
// compute matrix
CSML.Matrix weighted_mult_mat = new CSML.Matrix();
weighted_mult_mat = M_tr * W;
weighted_mult_mat = weighted_mult_mat * M;
var weighted_dense_mat = new DenseMatrix(3, 3);
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
weighted_dense_mat[i, j] = weighted_mult_mat[i + 1, j + 1].Re;
}
}
var weighted_svd = weighted_dense_mat.Svd(true);
var weighted_vt = weighted_svd.VT;
Vector3D weighted_dirVect = new Vector3D(weighted_vt[0, 0], weighted_vt[0, 1], weighted_vt[0, 2]);
weighted_dirVect.Normalize();
return weighted_dirVect;
}
public static Vector3D LinearRegression(List<Point3D> pts) {
Point3D avg = pts.average();
// populate Matrix M
CSML.Matrix M = new CSML.Matrix(pts.Count, 3); // init
// populate matrix M
for (int i = 1; i < pts.Count + 1; i++) {
M[i, 1] = new Complex(pts[i - 1].X - avg.X);
M[i, 2] = new Complex(pts[i - 1].Y - avg.Y);
M[i, 3] = new Complex(pts[i - 1].Z - avg.Z);
}
CSML.Matrix M_tr = M.Transpose();
CSML.Matrix mult_mat = new CSML.Matrix();
mult_mat = M_tr * M;
var dense_mat = new DenseMatrix(3, 3);
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
dense_mat[i, j] = mult_mat[i + 1, j + 1].Re ;
}
}
var svd = dense_mat.Svd(true);
var vt = svd.VT;
Vector3D dirVect = new Vector3D(vt[0, 0], vt[0, 1], vt[0, 2]);
dirVect.Normalize();
return dirVect;
}
I need to calculate matrix: ( X^(T) * X )^(-1).
Legend for the code&comments:
x is double[,] array;
xT - transposed matrix
^(-1) - inverted matrix
Every time i generate new random matrix to work with it and i found out that program is very unstable, because it isn't working properly with any input data. I'm sure about that because i need to get Identity matrix in the end if everything's fine, but sometimes i get a totally terrible Ineverted matrix so i don't get an Identity matrix. I'm dissappointes because i always use the same type of data and do not convert anything. Compiler is MVS 2010. Hope You will help me.
Here is my Program.cs:
static void Main(string[] args)
{
Matrix x = new Matrix(5, 4);
//Matrix temp = new Matrix(x.Row, x.Col);
//double[] y = new double[x.Row];
//double[] b = new double[x.Row];
//this data isn't calculated correctly. used for debugging
x.MatrixX[0, 0] = 7; x.MatrixX[0, 1] = 6; x.MatrixX[0, 2] = 5; x.MatrixX[0, 3] = 8;
x.MatrixX[1, 0] = 7; x.MatrixX[1, 1] = 5; x.MatrixX[1, 2] = 8; x.MatrixX[1, 3] = 5;
x.MatrixX[2, 0] = 6; x.MatrixX[2, 1] = 8; x.MatrixX[2, 2] = 6; x.MatrixX[2, 3] = 8;
x.MatrixX[3, 0] = 8; x.MatrixX[3, 1] = 5; x.MatrixX[3, 2] = 8; x.MatrixX[3, 3] = 7;
x.MatrixX[4, 0] = 8; x.MatrixX[4, 1] = 5; x.MatrixX[4, 2] = 6; x.MatrixX[4, 3] = 7;
/*
7,00000 6,00000 5,00000 8,00000
7,00000 5,00000 8,00000 5,00000
6,00000 8,00000 6,00000 8,00000
8,00000 5,00000 8,00000 7,00000
8,00000 5,00000 6,00000 7,00000
*/
//random matrix generation
/*
Random rnd = new Random();
for (int i = 0; i < x.Row; i++)
for (int j = 0; j < x.Col; j++)
x.MatrixX[i, j] = rnd.Next(5, 10);
*/
/*i'm going to calculate: ( X^(T) * X )^(-1)
* 1. transpose X
* 2. multiply X and (1)
* 3. invert matrix (2)
* +4. i wanna check the results: Multilate of (2) and (3) = Identity_matrix.
* */
Matrix.Display(x);
//1
Matrix xt = Matrix.Transpose(x);
Matrix.Display(xt);
//2
Matrix xxt = Matrix.Multiply(x, xt);
Matrix.Display(xxt);
//3
Matrix xxtinv = Matrix.Invert(Matrix.Multiply(x, xt));
Matrix.Display(xxtinv);
//4
Console.WriteLine("Invert(xxt) * xxt. IdentityMatrix:");
Matrix IdentityMatrix = Matrix.Multiply(xxtinv, xxt);
Matrix.Display(IdentityMatrix);
Console.ReadKey();
}
And here is Matrix.cs with all functions:
public class Matrix
{
private double[,] matrix;
private int row;
private int col;
#region constructors
public Matrix(int Row, int Col)
{
this.row = Row;
this.col = Col;
matrix = new double[Row, Col];
}
public Matrix()
{
Random rnd = new Random();
Row = rnd.Next(3, 7);
Col = rnd.Next(3, 7);
matrix = new double[Row, Col];
for (int i = 0; i < Row; i++)
for (int j = 0; j < Col; j++)
matrix[i, j] = rnd.Next(5, 10);
}
public Matrix(Matrix a)
{
this.Col = a.Col;
this.Row = a.Row;
this.matrix = a.matrix;
}
#endregion
#region properties
public int Col
{
get { return col; }
set { col = value; }
}
public int Row
{
get { return row; }
set { row = value; }
}
public double[,] MatrixX
{
get { return matrix; }
set { matrix = value; }
}
#endregion
static public Matrix Transpose(Matrix array)
{
Matrix temp = new Matrix(array.Col, array.Row);
for (int i = 0; i < array.Row; i++)
for (int j = 0; j < array.Col; j++)
temp.matrix[j, i] = array.matrix[i, j];
return temp;
}
static public void Display(Matrix array)
{
for (int i = 0; i < array.Row; i++)
{
for (int j = 0; j < array.Col; j++)
Console.Write("{0,5:f2}\t", array.matrix[i, j]);
Console.WriteLine();
}
Console.WriteLine();
}
static public Matrix Multiply(Matrix a, Matrix b)
{
if (a.Col != b.Row) throw new Exception("multiplication is impossible: a.Col != b.Row");
Matrix r = new Matrix(a.Row, b.Col);
for (int i = 0; i < a.Row; i++)
{
for (int j = 0; j < b.Col; j++)
{
double sum = 0;
for (int k = 0; k < b.Row; k++)
sum += a.matrix[i, k] * b.matrix[k, j];
r.matrix[i, j] = sum;
}
}
return r;
}
static public Matrix Invert(Matrix a)
{
Matrix E = new Matrix(a.Row, a.Col);
double temp = 0;
int n = a.Row;
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
{
E.matrix[i, j] = 0.0;
if (i == j)
E.matrix[i, j] = 1.0;
}
for (int k = 0; k < n; k++)
{
temp = a.matrix[k, k];
for (int j = 0; j < n; j++)
{
a.matrix[k, j] /= temp;
E.matrix[k, j] /= temp;
}
for (int i = k + 1; i < n; i++)
{
temp = a.matrix[i, k];
for (int j = 0; j < n; j++)
{
a.matrix[i, j] -= a.matrix[k, j] * temp;
E.matrix[i, j] -= E.matrix[k, j] * temp;
}
}
}
for (int k = n - 1; k > 0; k--)
{
for (int i = k - 1; i >= 0; i--)
{
temp = a.matrix[i, k];
for (int j = 0; j < n; j++)
{
a.matrix[i, j] -= a.matrix[k, j] * temp;
E.matrix[i, j] -= E.matrix[k, j] * temp;
}
}
}
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
{
a.matrix[i, j] = E.matrix[i, j];
}
return a;
}
}
In your example, the determinant of x * transpose(x) is zero. As a result, there is no inverse, which is probably why you're getting strange results.
I also note that your Inverse function modifies the matrix passed to it. This should probably be modified to avoid that.
int[] arr = {800,11,50,771,649,770,240, 9};
int temp = 0;
for (int write = 0; write < arr.Length; write++)
{
for (int sort = 0; sort < arr.Length - 1; sort++)
{
if (arr[sort] > arr[sort + 1])
{
temp = arr[sort + 1];
arr[sort + 1] = arr[sort];
arr[sort] = temp;
}
}
Console.Write("{0} ", arr[write]);
}
All I am attempting to do is a simple bubble sort with this array. I would like to figure out why the sorting is screwed up.
In example, here is when the array is {800,11,50,771,649,770,240, 9}:
Here is what gets displayed: 11, 50, 649, 9, 649, 770, 771, 800
I am thinking that I might be missing something in the comparison.
No, your algorithm works but your Write operation is misplaced within the outer loop.
int[] arr = { 800, 11, 50, 771, 649, 770, 240, 9 };
int temp = 0;
for (int write = 0; write < arr.Length; write++) {
for (int sort = 0; sort < arr.Length - 1; sort++) {
if (arr[sort] > arr[sort + 1]) {
temp = arr[sort + 1];
arr[sort + 1] = arr[sort];
arr[sort] = temp;
}
}
}
for (int i = 0; i < arr.Length; i++)
Console.Write(arr[i] + " ");
Console.ReadKey();
This one works for me
public static int[] SortArray(int[] array)
{
int length = array.Length;
int temp = array[0];
for (int i = 0; i < length; i++)
{
for (int j = i+1; j < length; j++)
{
if (array[i] > array[j])
{
temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
}
return array;
}
public static void BubbleSort(int[] a)
{
for (int i = 1; i <= a.Length - 1; ++i)
for (int j = 0; j < a.Length - i; ++j)
if (a[j] > a[j + 1])
Swap(ref a[j], ref a[j + 1]);
}
public static void Swap(ref int x, ref int y)
{
int temp = x;
x = y;
y = temp;
}
int[] arr = { 800, 11, 50, 771, 649, 770, 240, 9 };
int temp = 0;
for (int write = 0; write < arr.Length; write++)
{
for (int sort = 0; sort < arr.Length - 1 - write ; sort++)
{
if (arr[sort] > arr[sort + 1])
{
temp = arr[sort + 1];
arr[sort + 1] = arr[sort];
arr[sort] = temp;
}
}
}
for (int i = 0; i < arr.Length; i++) Console.Write(arr[i] + " ");
Console.ReadKey();
I saw someone use this example as part of a job application test. My feedback to him was that it lacks an escape from the outer loop when the array is mostly sorted.
consider what would happen in this case:
int[] arr = {1,2,3,4,5,6,7,8};
here's something that makes more sense:
int[] arr = {1,2,3,4,5,6,7,8};
int temp = 0;
int loopCount=0;
bool doBreak=true;
for (int write = 0; write < arr.Length; write++)
{
doBreak=true;
for (int sort = 0; sort < arr.Length - 1; sort++)
{
if (arr[sort] > arr[sort + 1])
{
temp = arr[sort + 1];
arr[sort + 1] = arr[sort];
arr[sort] = temp;
doBreak=false;
}
loopCount++;
}
if(doBreak){ break; /*early escape*/ }
}
Console.WriteLine(loopCount);
for (int i = 0; i < arr.Length; i++) Console.Write(arr[i] + " ");
public static int[] BubbleSort(int[] arr)
{
int length = arr.Length();
while (length > 0)
{
int newLength = 0;
for (int i = 1; i < length; i++)
{
if (arr[i - 1] > arr[i])
{
Swap(ref arr[i - 1], ref arr[i]);
newLength = i;
}
}
length = newLength;
}
}
public static void Swap(ref int x, ref int y)
{
int temp = y;
y = x;
x = temp;
}
I wanted to add to the accepted answer something different:
Number of iterations can be reduced as well, as below.
int[] arr = { 800, 11, 50, 771, 649, 770, 240, 9 };
int temp = 0;
int arrLength = arr.Length;
for (int write = 0; write < arr.Length - 1; write++, arrLength--)
{
for (int sort = 0; sort < arrLength - 1; sort++)
{
if (arr[sort] > arr[sort + 1])
{
temp = arr[sort + 1];
arr[sort + 1] = arr[sort];
arr[sort] = temp;
}
}
}
foreach (var item in arr)
{
Console.WriteLine(item);
}
Your Console.Write("{0} ", arr[write]); is too early. You're printing the values while the sort is still in progress. For example, you're printing 9 as being index 3 in the array, yet on the very next iteration of the loop the 9 has moved to index 2 and 240 has moved to index 3... yet you're outer loop has moved forward so it prints 649 the second time and 240 never gets printed.
int[] array = new int[10] { 13, 2, 5, 8, 23, 90, 41, 4, 77, 61 };
for (int i = 10; i > 0; i--)
{
for (int j = 0; j < 9; j++)
{
if (array[j] > array[j + 1])
{
int temp = array[j];
array[j] = array[j + 1];
array[j + 1] = temp;
}
}
}
static bool BubbleSort(ref List<int> myList, int number)
{
if (number == 1)
return true;
for (int i = 0; i < number; i++)
{
if ((i + 1 < number) && (myList[i] > myList[i + 1]))
{
int temp = myList[i];
myList[i] = myList[i + 1];
myList[i + 1] = temp;
}
else
continue;
}
return BubbleSort(ref myList, number - 1);
}
Just another example but with an outter WHILE loop instead of a FOR:
public static void Bubble()
{
int[] data = { 5, 4, 3, 2, 1 };
bool newLoopNeeded = false;
int temp;
int loop = 0;
while (!newLoopNeeded)
{
newLoopNeeded = true;
for (int i = 0; i < data.Length - 1; i++)
{
if (data[i + 1] < data[i])
{
temp = data[i];
data[i] = data[i + 1];
data[i + 1] = temp;
newLoopNeeded = false;
}
loop++;
}
}
}
Bubble sort with sort direction -
using System;
public class Program
{
public static void Main(string[] args)
{
var input = new[] { 800, 11, 50, 771, 649, 770, 240, 9 };
BubbleSort(input);
Array.ForEach(input, Console.WriteLine);
Console.ReadKey();
}
public enum Direction
{
Ascending = 0,
Descending
}
public static void BubbleSort(int[] input, Direction direction = Direction.Ascending)
{
bool swapped;
var length = input.Length;
do
{
swapped = false;
for (var index = 0; index < length - 1; index++)
{
var needSwap = direction == Direction.Ascending ? input[index] > input[index + 1] : input[index] < input[index + 1];
if (needSwap)
{
var temp = input[index];
input[index] = input[index + 1];
input[index + 1] = temp;
swapped = true;
}
}
} while (swapped);
}
}
This is what I wrote using recursive methods:
public static int[] BubbleSort(int[] input)
{
bool isSorted = true;
for (int i = 0; i < input.Length; i++)
{
if (i != input.Length - 1 && input[i] > input[i + 1])
{
isSorted = false;
int temp = input[i];
input[i] = input[i + 1];
input[i + 1] = temp;
}
}
return isSorted ? input : BubbleSort(input);
}
It does the same in a more elegant way.
var arrayValues = new[] { 99, 12, 11, 300, 400, 10, 9, 3, 6, 5, 7, 8};
for (var mainLoop = 0; mainLoop < arrayValues.Length; mainLoop++)
{
for (var innerLoop = mainLoop + 1; innerLoop < arrayValues.Length; innerLoop++)
{
if (arrayValues[mainLoop] <= arrayValues[innerLoop])
{
continue;
}
var temp = arrayValues[mainLoop];
arrayValues[mainLoop] = arrayValues[innerLoop];
arrayValues[innerLoop] = temp;
}
}
So i did mine as a recursive function (no need for the nested loop), perhaps someone could comment if this is inefficient (when compared to the other solutions).
public static int[] BubbleSort(int[] arrayOfValues)
{
var swapOccurred = false;
for (var i = 0; i < arrayOfValues.Length; i++)
{
if (i == arrayOfValues.Length - 1)
continue;
if (arrayOfValues[i] > arrayOfValues[i + 1])
{
//swap values
var current = arrayOfValues[i];
var next = arrayOfValues[i + 1];
arrayOfValues[i] = next;
arrayOfValues[i + 1] = current;
swapOccurred = true;
}
}
if (swapOccurred)
{
// keep going until no further swaps are required:
BubbleSort(arrayOfValues);
}
return arrayOfValues;
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Practice {
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Enter the size");
int n = Convert.ToInt32(Console.ReadLine());
int[] mynum = new int[n];
Console.WriteLine("Enter the Numbers");
for (int p = 0; p < n;p++ )
{
mynum[p] = Convert.ToInt32(Console.ReadLine());
}
Console.WriteLine("The number are");
foreach(int p in mynum)
{
Console.WriteLine(p);
}
for (int i = 0; i < n;i++ )
{
for(int j=i+1;j<n;j++)
{
if(mynum[i]>mynum[j])
{
int x = mynum[j];
mynum[j] = mynum[i];
mynum[i] = x;
}
}
}
Console.WriteLine("Sortrd data is-");
foreach(int p in mynum)
{
Console.WriteLine(p);
}
Console.ReadLine();
}
} }
int[] arr = { 800, 11, 50, 771, 649, 770, 240, 9 };
for (int i = 0; i < arr.Length; i++)
{
for (int j = i; j < arr.Length ; j++)
{
if (arr[j] < arr[i])
{
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
}
Console.ReadLine();
public void BubbleSortNum()
{
int[] a = {10,5,30,25,40,20};
int length = a.Length;
int temp = 0;
for (int i = 0; i <length; i++)
{
for(int j=i;j<length; j++)
{
if (a[i]>a[j])
{
temp = a[j];
a[j] = a[i];
a[i] = temp;
}
}
Console.WriteLine(a[i]);
}
}