How can I create an array and populate it in the hint Cairo lang/Protostar?

There are two examples I found, that can work:

Example 1

Simply add a hint:

let (local result : felt*) = alloc()
    %{ segments.write_arg(ids.result, [1, 2, 3]) %}

Example 2

This example proposed by Lord Cairo:

%{
        IDENTIFIER_INDEX = 1
        ADJACENT_VERTICES_INDEX = 2
        for i in range(ids.graph_len):
            neighbours_len = memory[ids.adjacent_vertices_count+i]
            vertex_id = memory[ids.vertices.address_+i*ids.Vertex.SIZE+IDENTIFIER_INDEX]
            adjacent_vertices_pointer = memory[ids.vertices.address_+i*ids.Vertex.SIZE+ADJACENT_VERTICES_INDEX]
            print(f"{vertex_id} -> {{",end='')
            for j in range (neighbours_len):
                adjacent_vertex = memory[adjacent_vertices_pointer+j*ids.AdjacentVertex.SIZE+IDENTIFIER_INDEX]
                print(f"{adjacent_vertex} ",end='')
            print('}',end='')
            print()
    %}