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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace dijkstra
{
class Program
{
 static void Main(string[] args)
 {
 int n = 5; //nodes
 int m = 100; //square
 int mm = 999; //max cost
 double t = m / 2; //distance
 float[] x, y; //x and y coordinates
 x = new float[n + 1];
 y = new float[n + 1];
 float[,] c; //cost matrix
 c = new float[n + 1, n + 1];
 int[,] a; //adjacency matrix
 a = new int[n + 1, n + 1];
 //distance array
 float[] d;
 d = new float[n + 1];
 //span array 
 int[] sa;
 sa = new int[n + 1];
 Random r = new Random();
 //randomise coordinates
 for (int i = 1; i <= n; i++)
 {
 x[i] = m * (float)r.NextDouble();
 y[i] = m * (float)r.NextDouble();
 d[i] = mm;
 sa[i] = 0;
 }
 //coordinates
 Console.WriteLine("Coordinates");
 for (int i = 1; i <= n; i++)
 Console.WriteLine(i + ": (" + x[i].ToString("0.00") + " , " + y[i].ToString("0.00") + " )");
 Console.WriteLine();
 //span array
 Console.WriteLine("Spanne array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 //calculate distance costs
 for (int i = 1; i <= n; i++)
 for (int j = i + 1; j <= n; j++)
 {
 c[i, j] = (float)Math.Sqrt((x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]));
 if (c[i, j] > t)
 c[i, j] = mm;
 a[i, j] = 0;
 }
 Console.WriteLine("Starting values: ");
 Console.WriteLine();
 // distances
 Console.WriteLine("Cost matrix");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if ((i >= j) || (c[i, j] > t)) //if i is greater than j or is the 999 distance then
 Console.Write(" -- ");
 else
 Console.Write(" " + c[i, j].ToString("00.00"));
 Console.WriteLine();
 }
 Console.WriteLine();
 //adjaceny matrics
 Console.WriteLine("Adjancency matrix");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if (i >= j)
 Console.Write(" -");
 else
 Console.Write(" " + a[i, j]);
 Console.WriteLine();
 }
 Console.WriteLine();
 Console.ReadLine();
 // starting node
 int start = r.Next(1, n + 1);
 Console.WriteLine("Start at node " + start + " ...");
 Console.WriteLine();
 sa[start] = 1;
 d[start] = 0;
 Console.WriteLine("Span array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.WriteLine("Distance array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + d[i].ToString("0.00") + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.ReadLine();
 for (int k = 1; k < n; k++)
 {
 float shortestDistance = mm;
 int iShortest = 0, jShortest = 0, spannedShortest = 0, unspannedShortest = 0;
 for (int i = 1; i < n; i++)
 for (int j = i + 1; j <= n; j++)
 if ((sa[i] == 1) && (sa[j] == 0))
 {
 if (d[i] + c[i, j] < shortestDistance)
 {
 shortestDistance = d[i] + c[i, j];
 iShortest = i;
 jShortest = j;
 spannedShortest = i;
 unspannedShortest = j;
 }
 }
 else if ((sa[i] == 0) && (sa[j] == 1))
 {
 if (d[j] + c[i, j] < shortestDistance)
 {
 shortestDistance = d[j] + c[i, j];
 iShortest = i;
 jShortest = j;
 spannedShortest = j;
 unspannedShortest = i;
 }
 }
 a[iShortest, jShortest] = 1;
 Console.WriteLine("Joining " + iShortest + " and " + jShortest);
 sa[unspannedShortest] = 1;
 d[unspannedShortest] = d[spannedShortest] + c[iShortest, jShortest];
 Console.WriteLine("Distance to " + unspannedShortest + " is " + d[unspannedShortest].ToString("00.00"));
 Console.ReadLine();
 }
 Console.WriteLine("Spanned array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.WriteLine("Adjancey array");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if (i >= j)
 Console.Write(" -");
 else
 Console.Write(" " + a[i, j]);
 Console.WriteLine();
 }
 Console.WriteLine();
 // look at the distance array
 Console.WriteLine("Distance array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + d[i].ToString("0.00") + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.ReadLine();
 }
 }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace dijkstra
{
class Program
{
 static void Main(string[] args)
 {
 int n = 5; //nodes
 int m = 100; //size of square
 int mm = 999; //maximum cost
 double t = m / 0.75; //distance
 float[] x, y; //x and y coordinates
 x = new float[n + 1];
 y = new float[n + 1];
 float[,] c; //cost matrix
 c = new float[n + 1, n + 1];
 int[,] a; //adjacency matrix
 a = new int[n + 1, n + 1];
 //distance array
 float[] d;
 d = new float[n + 1];
 //span array 
 int[] sa;
 sa = new int[n + 1];
 Random r = new Random();
 //randomise coordinates
 for (int i = 1; i <= n; i++)
 {
 x[i] = m * (float)r.NextDouble();
 y[i] = m * (float)r.NextDouble();
 d[i] = mm;
 sa[i] = 0;
 }
 //coordinates
 Console.WriteLine("Coordinates");
 for (int i = 1; i <= n; i++)
 Console.WriteLine(i + ": (" + x[i].ToString("0.00") + " , " + y[i].ToString("0.00") + " )");
 Console.WriteLine();
 //span array
 Console.WriteLine("Spanne array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 //calculate distance costs
 for (int i = 1; i <= n; i++)
 for (int j = i + 1; j <= n; j++)
 {
 c[i, j] = (float)Math.Sqrt((x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]));
 if (c[i, j] > t)
 c[i, j] = mm;
 a[i, j] = 0;
 }
 Console.WriteLine("Starting values: ");
 Console.WriteLine();
 // distances
 Console.WriteLine("Cost matrix");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if ((i >= j) || (c[i, j] > t)) //if i is greater than j or is the 999 distance then
 Console.Write(" -- ");
 else
 Console.Write(" " + c[i, j].ToString("00.00"));
 Console.WriteLine();
 }
 Console.WriteLine();
 //adjaceny matrics
 Console.WriteLine("Adjancency matrix");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if (i >= j)
 Console.Write(" -");
 else
 Console.Write(" " + a[i, j]);
 Console.WriteLine();
 }
 Console.WriteLine();
 Console.ReadLine();
 // starting node
 int start = r.Next(1, n + 1);
 Console.WriteLine("Start at node " + start + " ...");
 Console.WriteLine();
 sa[start] = 1;
 d[start] = 0;
 Console.WriteLine("Span array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.WriteLine("Distance array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + d[i].ToString("0.00") + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.ReadLine();
 for (int k = 1; k < n; k++)
 {
 float shortestDistance = mm;
 int iShortest = 0, jShortest = 0, spannedShortest = 0, unspannedShortest = 0;
 for (int i = 1; i < n; i++)
 for (int j = i + 1; j <= n; j++)
 if ((sa[i] == 1) && (sa[j] == 0))
 {
 if (d[i] + c[i, j] < shortestDistance)
 {
 shortestDistance = d[i] + c[i, j];
 iShortest = i;
 jShortest = j;
 spannedShortest = i;
 unspannedShortest = j;
 }
 }
 else if ((sa[i] == 0) && (sa[j] == 1))
 {
 if (d[j] + c[i, j] < shortestDistance)
 {
 shortestDistance = d[j] + c[i, j];
 iShortest = i;
 jShortest = j;
 spannedShortest = j;
 unspannedShortest = i;
 }
 }
 a[iShortest, jShortest] = 1;
 Console.WriteLine("Joining " + iShortest + " and " + jShortest);
 sa[unspannedShortest] = 1;
 d[unspannedShortest] = d[spannedShortest] + c[iShortest, jShortest];
 Console.WriteLine("Distance to " + unspannedShortest + " is " + d[unspannedShortest].ToString("00.00"));
 Console.ReadLine();
 }
 Console.WriteLine("Spanned array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.WriteLine("Adjancey array");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if (i >= j)
 Console.Write(" -");
 else
 Console.Write(" " + a[i, j]);
 Console.WriteLine();
 }
 Console.WriteLine();
 // look at the distance array
 Console.WriteLine("Distance array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + d[i].ToString("0.00") + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.ReadLine();
 }
 }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace dijkstra
{
class Program
{
 static void Main(string[] args)
 {
 int n = 5; //nodes
 int m = 100; //size of square
 int mm = 999; //maximum cost
 double t = m / 0.75; //distance
 float[] x, y; //x and y coordinates
 x = new float[n + 1];
 y = new float[n + 1];
 float[,] c; //cost matrix
 c = new float[n + 1, n + 1];
 int[,] a; //adjacency matrix
 a = new int[n + 1, n + 1];
 //distance array
 float[] d;
 d = new float[n + 1];
 //span array 
 int[] sa;
 sa = new int[n + 1];
 Random r = new Random();
 //randomise coordinates
 for (int i = 1; i <= n; i++)
 {
 x[i] = m * (float)r.NextDouble();
 y[i] = m * (float)r.NextDouble();
 d[i] = mm;
 sa[i] = 0;
 }
 //coordinates
 Console.WriteLine("Coordinates");
 for (int i = 1; i <= n; i++)
 Console.WriteLine(i + ": (" + x[i].ToString("0.00") + " , " + y[i].ToString("0.00") + " )");
 Console.WriteLine();
 //span array
 Console.WriteLine("Spanne array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 //calculate distance costs
 for (int i = 1; i <= n; i++)
 for (int j = i + 1; j <= n; j++)
 {
 c[i, j] = (float)Math.Sqrt((x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]));
 if (c[i, j] > t)
 c[i, j] = mm;
 a[i, j] = 0;
 }
 Console.WriteLine("Starting values: ");
 Console.WriteLine();
 // distances
 Console.WriteLine("Cost matrix");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if ((i >= j) || (c[i, j] > t)) //if i is greater than j or is the 999 distance then
 Console.Write(" -- ");
 else
 Console.Write(" " + c[i, j].ToString("00.00"));
 Console.WriteLine();
 }
 Console.WriteLine();
 //adjaceny matrics
 Console.WriteLine("Adjancency matrix");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if (i >= j)
 Console.Write(" -");
 else
 Console.Write(" " + a[i, j]);
 Console.WriteLine();
 }
 Console.WriteLine();
 Console.ReadLine();
 // starting node
 int start = r.Next(1, n + 1);
 Console.WriteLine("Start at node " + start + " ...");
 Console.WriteLine();
 sa[start] = 1;
 d[start] = 0;
 Console.WriteLine("Span array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.WriteLine("Distance array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + d[i].ToString("0.00") + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.ReadLine();
 for (int k = 1; k < n; k++)
 {
 float shortestDistance = mm;
 int iShortest = 0, jShortest = 0, spannedShortest = 0, unspannedShortest = 0;
 for (int i = 1; i < n; i++)
 for (int j = i + 1; j <= n; j++)
 if ((sa[i] == 1) && (sa[j] == 0))
 {
 if (d[i] + c[i, j] < shortestDistance)
 {
 shortestDistance = d[i] + c[i, j];
 iShortest = i;
 jShortest = j;
 spannedShortest = i;
 unspannedShortest = j;
 }
 }
 else if ((sa[i] == 0) && (sa[j] == 1))
 {
 if (d[j] + c[i, j] < shortestDistance)
 {
 shortestDistance = d[j] + c[i, j];
 iShortest = i;
 jShortest = j;
 spannedShortest = j;
 unspannedShortest = i;
 }
 }
 a[iShortest, jShortest] = 1;
 Console.WriteLine("Joining " + iShortest + " and " + jShortest);
 sa[unspannedShortest] = 1;
 d[unspannedShortest] = d[spannedShortest] + c[iShortest, jShortest];
 Console.WriteLine("Distance to " + unspannedShortest + " is " + d[unspannedShortest].ToString("00.00"));
 Console.ReadLine();
 }
 Console.WriteLine("Spanned array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.WriteLine("Adjancey array");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if (i >= j)
 Console.Write(" -");
 else
 Console.Write(" " + a[i, j]);
 Console.WriteLine();
 }
 Console.WriteLine();
 // look at the distance array
 Console.WriteLine("Distance array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + d[i].ToString("0.00") + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.ReadLine();
 }
 }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace dijkstra
{
class Program
{
 static void Main(string[] args)
 {
 int n = 5; //nodes
 int m = 100; //square
 int mm = 999; //max cost
 double t = m / 2; //distance
 float[] x, y; //x and y coordinates
 x = new float[n + 1];
 y = new float[n + 1];
 float[,] c; //cost matrix
 c = new float[n + 1, n + 1];
 int[,] a; //adjacency matrix
 a = new int[n + 1, n + 1];
 //distance array
 float[] d;
 d = new float[n + 1];
 //span array 
 int[] sa;
 sa = new int[n + 1];
 Random r = new Random();
 //randomise coordinates
 for (int i = 1; i <= n; i++)
 {
 x[i] = m * (float)r.NextDouble();
 y[i] = m * (float)r.NextDouble();
 d[i] = mm;
 sa[i] = 0;
 }
 //coordinates
 Console.WriteLine("Coordinates");
 for (int i = 1; i <= n; i++)
 Console.WriteLine(i + ": (" + x[i].ToString("0.00") + " , " + y[i].ToString("0.00") + " )");
 Console.WriteLine();
 //span array
 Console.WriteLine("Spanne array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 //calculate distance costs
 for (int i = 1; i <= n; i++)
 for (int j = i + 1; j <= n; j++)
 {
 c[i, j] = (float)Math.Sqrt((x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]));
 if (c[i, j] > t)
 c[i, j] = mm;
 a[i, j] = 0;
 }
 Console.WriteLine("Starting values: ");
 Console.WriteLine();
 // distances
 Console.WriteLine("Cost matrix");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if ((i >= j) || (c[i, j] > t)) //if i is greater than j or is the 999 distance then
 Console.Write(" -- ");
 else
 Console.Write(" " + c[i, j].ToString("00.00"));
 Console.WriteLine();
 }
 Console.WriteLine();
 //adjaceny matrics
 Console.WriteLine("Adjancency matrix");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if (i >= j)
 Console.Write(" -");
 else
 Console.Write(" " + a[i, j]);
 Console.WriteLine();
 }
 Console.WriteLine();
 Console.ReadLine();
 // starting node
 int start = r.Next(1, n + 1);
 Console.WriteLine("Start at node " + start + " ...");
 Console.WriteLine();
 sa[start] = 1;
 d[start] = 0;
 Console.WriteLine("Span array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.WriteLine("Distance array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + d[i].ToString("0.00") + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.ReadLine();
 for (int k = 1; k < n; k++)
 {
 float shortestDistance = mm;
 int iShortest = 0, jShortest = 0, spannedShortest = 0, unspannedShortest = 0;
 for (int i = 1; i < n; i++)
 for (int j = i + 1; j <= n; j++)
 if ((sa[i] == 1) && (sa[j] == 0))
 {
 if (d[i] + c[i, j] < shortestDistance)
 {
 shortestDistance = d[i] + c[i, j];
 iShortest = i;
 jShortest = j;
 spannedShortest = i;
 unspannedShortest = j;
 }
 }
 else if ((sa[i] == 0) && (sa[j] == 1))
 {
 if (d[j] + c[i, j] < shortestDistance)
 {
 shortestDistance = d[j] + c[i, j];
 iShortest = i;
 jShortest = j;
 spannedShortest = j;
 unspannedShortest = i;
 }
 }
 a[iShortest, jShortest] = 1;
 Console.WriteLine("Joining " + iShortest + " and " + jShortest);
 sa[unspannedShortest] = 1;
 d[unspannedShortest] = d[spannedShortest] + c[iShortest, jShortest];
 Console.WriteLine("Distance to " + unspannedShortest + " is " + d[unspannedShortest].ToString("00.00"));
 Console.ReadLine();
 }
 Console.WriteLine("Spanned array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + sa[i] + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.WriteLine("Adjancey array");
 for (int i = 1; i <= n; i++)
 {
 for (int j = 1; j <= n; j++)
 if (i >= j)
 Console.Write(" -");
 else
 Console.Write(" " + a[i, j]);
 Console.WriteLine();
 }
 Console.WriteLine();
 // look at the distance array
 Console.WriteLine("Distance array");
 for (int i = 1; i <= n; i++)
 Console.Write(i + ": " + d[i].ToString("0.00") + " ");
 Console.WriteLine();
 Console.WriteLine();
 Console.ReadLine();
 }
 }
}

I have implementing a simple version of Dijkstra's algorithm in C#. I found it really confusing, and I'm not 100% if I've implemented it correctly. Could this be made more efficient? Does it need to be modified?

I have implementing a simple version of Dijkstra's algorithm in C#. Could this be made more efficient? Does it need to be modified?