Dijkstra in C#

Dijkstra

in C#

Welcome to the Dijkstra in C# page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

if (
    args is not [var matrixRaw, var sourceRaw, var destRaw]
    || !int.TryParse(sourceRaw, out int source)
    || !int.TryParse(destRaw, out int dest)
    || !TryParseList(matrixRaw.AsSpan(), out var matrix)
)
    return Usage();

int n = (int)Math.Sqrt(matrix.Count);
if (n * n != matrix.Count || (uint)source >= n || (uint)dest >= n)
    return Usage();

var graph = new List<(int, uint)>[n];
for (int i = 0; i < n; i++)
    graph[i] = [];

for (int u = 0, k = 0; u < n; u++)
    for (int v = 0; v < n; v++, k++)
        if (matrix[k] != 0)
            graph[u].Add((v, (uint)matrix[k]));

uint result = Dijkstra(graph, source, dest);
if (result == uint.MaxValue)
    return Usage();

Console.WriteLine(result);
return 0;

static uint Dijkstra(List<(int to, uint w)>[] graph, int source, int destination)
{
    var dist = new uint[graph.Length];
    Array.Fill(dist, uint.MaxValue);

    var pq = new PriorityQueue<int, uint>();
    pq.Enqueue(source, dist[source] = 0);

    while (pq.TryDequeue(out int u, out uint d))
    {
        if (d != dist[u])
            continue;
        if (u == destination)
            return d;

        foreach (var (v, w) in graph[u])
        {
            uint newDist = d + w;
            if (newDist < dist[v])
                pq.Enqueue(v, dist[v] = newDist);
        }
    }

    return uint.MaxValue;
}

static bool TryParseList(ReadOnlySpan<char> span, out List<int> numbers)
{
    numbers = new(span.Count(',') + 1);

    while (!span.IsEmpty)
    {
        int comma = span.IndexOf(',');
        var token = comma >= 0 ? span[..comma] : span;

        span = comma >= 0 ? span[(comma + 1)..] : [];

        if (!int.TryParse(token, out int n) || n < 0)
            return false;

        numbers.Add(n);
    }

    return true;
}

static int Usage()
{
    Console.Error.WriteLine(
        "Usage: please provide three inputs: a serialized matrix, a source node and a destination node"
    );
    return 1;
}

Dijkstra in C# was written by:

• Ștefan-Iulian Alecu

If you see anything you'd like to change or update, please consider contributing.

How to Implement the Solution

No 'How to Implement the Solution' section available. Please consider contributing.

How to Run the Solution

No 'How to Run the Solution' section available. Please consider contributing.