Mapping vertices to an index

[coarse cape]

I am trying to implement dijkstras algorithm, to find the shortest path in a graph of vertices. I have looked at this C-implementation from rosetttacode: https://rosettacode.org/wiki/Dijkstra's_algorithm#C

In this implementation, the vertices are added to the graph array through this function

void add_vertex (graph_t *g, int i) {
    if (g->vertices_size < i + 1) {
        int size = g->vertices_size * 2 > i ? g->vertices_size * 2 : i + 4;
        g->vertices = realloc(g->vertices, size * sizeof (vertex_t *));
        for (int j = g->vertices_size; j < size; j++)
            g->vertices[j] = NULL;
        g->vertices_size = size;
    }
    if (!g->vertices[i]) {
        g->vertices[i] = calloc(1, sizeof (vertex_t));
        g->vertices_len++;
    }
}

My question is in regards to the second if statement, where the function checks if a vertex is already in the array. In the implementation, vertices are named from a-z, making it easy to map a vertex to an index: int v = a - 'a'. In my case however, there is more vertices than 26 vertices, and they would have a name field in the vertex struct. How would I map a vertex to an index in this case? My only idea is to do it through a hashmap, but maybe there is a more elegant solution. Let me know if I need to clarify, thanks 🙂

[terse shore]

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[coarse cape]

Basically I need to map a string to a number such that: "supermarket" = 0, "busstop" = 1, "cinema" = 3 and so on

[chilly bay]

do you know all the names at compile time?

then you can use an enum

so each vertex would store an enum value instead of a name

[coarse cape]

no, I should have mentioned that the vertices are unknown at compile time

[chilly bay]

then a hashmap probably makes sense, yeah

or you could store the int in the node itself