Dijkstra implementation in Kotlin language

dijkstra.kt

private const val startPoint = "A"
private const val finalPoint = "G"

data class Vertex(val id: String, val length: Int)

// adjacency list graph
val graph =
    mapOf(
        "A" to listOf(Vertex("B", 3), Vertex("C", 5)),
        "B" to listOf(Vertex("A", 3), Vertex("D", 4), Vertex("E", 2)),
        "C" to listOf(Vertex("A", 5), Vertex("D", 3)),
        "D" to listOf(Vertex("C", 3), Vertex("B", 4)),
        "E" to listOf(Vertex("B", 2), Vertex("F", 2), Vertex("G", 3)),
        "F" to listOf(Vertex("E", 2), Vertex("G", 2)),
        "G" to listOf(Vertex("F", 2), Vertex("E", 3)),
    )

data class Item(
    val id: String,
    var length: Int = Int.MAX_VALUE,
    var bestPath: List<String> = emptyList()
)

fun main() {
    // initialize priority queue
    val queue = graph
        .map { Item(it.key, if (it.key == startPoint) 0 else Int.MAX_VALUE) }
        .toMutableList()

    // while target is not on top of priority queue
    while (queue[0].id != finalPoint) {

        // remove item from priority queue
        val item = queue.removeAt(0)
        graph[item.id]!!.forEach { edge ->

            val neighbor = queue.firstOrNull { it.id == edge.id } ?: return@forEach

            // compute new distance from $item to $neighbor following $edge
            val alt = edge.length + item.length

            // update priority queue if new distance is smaller than actual
            if (neighbor.length > alt) {
                neighbor.length = alt
                neighbor.bestPath = item.bestPath + edge.id
            }
        }
        queue.sortBy { it.length }
    }

    println("Shortest distance from $startPoint to $finalPoint is ${queue[0].length}")
    println(queue[0].bestPath.joinToString(" -> "))
}