DecimalTreeInsertion.swift

class DecimalSearchTree{
    ...
    
    func insert(number: String, data: Any) {
        // Insert the data in order of the number to the Decimal Search Tree
        // recursively.
        insertNodeRecursive(number: number, data: data, node: self.root)
    }
    
    func insertNodeRecursive(number: String, data: Any, node: DecimalTreeNode) {
        // Helper function for insert
        
        // Check if the program has done traversing
        if number.count == 0 {
            // Insert the data is there aren't any
            if node.data == nil {
                node.data = data
                self.usedSize += 1
            }
            return
        }
        
        let nextIndex = Int(String(number.prefix(1)))
        let remainder = String(number.dropFirst())
        
        if node.next[nextIndex!] == nil {
            node.next[nextIndex!] = DecimalTreeNode(data: nil)
            self.size += 10
        }
        
        insertNodeRecursive(number: remainder, data: data, node: node.next[nextIndex!]!)
    }
}