Graph data structure in Swift using an Adjacency Matrix.

GraphAM.swift

public struct GraphAM {
    private var adjMatrix = [[Int?]]()
    private var numberOfVertices: Int {
        return adjMatrix.count
    }

    init(numberOfVertices: Int) {
        adjMatrix = Array(repeating: Array(repeating: nil, count: numberOfVertices), count: numberOfVertices)
    }
    
    public mutating func addEdge(from source: Int, to destination: Int, with weight: Int? = nil) {
        adjMatrix[source][destination] = weight ?? 1
    }
    
    public mutating func removeEdge(from source: Int, to destination: Int) {
        if source < numberOfVertices && destination < numberOfVertices {
            adjMatrix[source][destination] = nil
            adjMatrix[destination][source] = nil
        }
    }
    
    public func isEdge(from source: Int, to destination: Int) -> Bool {
        return adjMatrix[source][destination] != nil
    }
}