PrefixTreeNode.swift

class PrefixTreeNode {
    var data: String?
    var weight: Int = 0
    var userWeight: Int?
    var children: [PrefixTreeNode?] = Array(repeating: nil, count: 26)
    
    func isEmpty() -> Bool {
        return self.numberOfChildren() == 0
    }
    
    func numberOfChildren() -> Int {
        // Return the number of non nil children in the array
        return children.reduce(0, { result, child in return child == nil ? result : result + 1 })
    }
    
    private func hasChild(_ char: Character) -> Bool {
        // Return a bool whether the node has a child for the given character
        if char.isLetter {
            let value = self.charToInt(char)
            return self.children[value - 65] != nil
        } else {
            return false
        }
    }
    
    func getChild(_ char: Character) -> PrefixTreeNode? {
        // Return the child node for the given character
        return self.hasChild(char) ? self.children[self.charToInt(char) - 65] : nil
    }
    
    func addChild(_ char: Character, childNode: PrefixTreeNode) {
        if !self.hasChild(char) && char.isLetter {
            self.children[self.charToInt(char) - 65] = childNode
        }
    }
    
    private func charToInt(_ char: Character) -> Int {
        if let value = char.asciiValue {
            return Int(value)
        } else {
            return -1
        }
    }
}