Dijkstra algorithm C#

Question

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

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();
 }
 }
}

• Mast: Please do not update the code in your question to incorporate feedback from answers, doing so goes against the Question + Answer style of Code Review. This is not a forum where you should keep the most updated version in your question. Please see what you may and may not do after receiving answers .
• greybeard: (There are spelling errors in the prompts.)
• greybeard: Hm. What square, what spans?

Answer 1

Symbolic Constants
It is good that you named these numeric constants, but they are constants so rather than declare them as variables, declare them as constants.

 static void Main(string[] args)
 {
 const int n = 5; //nodes
 const int m = 100; //size of square
 const int mm = 999; //maximum cost
 const double t = m / 0.75; //distance

DRY Code
There is a programming principle called the Don't Repeat Yourself Principle sometimes referred to as DRY code. If you find yourself repeating the same code multiple times it is better to encapsulate it in a function. If it is possible to loop through the code that can reduce repetition as well.

This code is almost repeating and can be encapsulated in a function.

 {
 shortestDistance = d[i] + c[i, j];
 iShortest = i;
 jShortest = j;
 spannedShortest = i;
 unspannedShortest = j;
 }

Other code that could be put into a function is the code that prints out the arrays.

Use Functions to Break Up the Code
When designing and writing software the best problem solving method is to decompose the problem into smaller and smaller parts. This makes coding much easier and limits the complexity of the code. One example is the code above that is reusable. Smaller blocks of code are easier to read, write, debug and maintain.

Format the Output
There are ways to format Console.Write() and Console.WriteLine():

 Console.WriteLine("Coordinates");
 for (int i = 1; i <= n; i++)
 {
 Console.WriteLine("{0:D}: ({1:F}, {2:F})", i, x[i].ToString("0.00"), y[i].ToString("0.00"));
 }
 Console.WriteLine();

Rather than using Console.WriteLine(); use Console.WriteLine("\n"); or Console.Write("\n\n"); to insert blank lines.

This is a beginning and I'm out of time. After you have made functions you might want to post a second question with a link to this one.