/// <summary>
/// Performs a simplified SQL-style LEFT JOIN operation on two hash tables
/// </summary>
/// <param name="ht1">left hash table</param>
/// <param name="ht2">right hash table</param>
/// <returns>list of arrays</returns>
public static List <string[]> LeftJoin(Hashtable ht1, Hashtable ht2)
{
// Initialize list of arrays
List <string[]> listOfArrays = new List <string[]>();
// Traverse left hash table
for (int i = 0; i < ht1.Map.Length; i++)
{
if (ht1.Map[i] != null)
{
foreach (var node in ht1.Map[i])
{
Node ht1Node = ht1.Get(node.Key);
// Initialize new array to hold current table row's contents
string[] array = new string[3];
// Populate array's first two indices with key and value from left table
array[0] = ht1Node.Key;
array[1] = ht1Node.Value;
if (ht2.Contains(ht1Node.Key))
{
Node ht2Node = ht2.Get(ht1Node.Key);
array[2] = ht2Node.Value;
}
else
{
array[2] = "NULL";
}
listOfArrays.Add(array);
}
}
}
return(listOfArrays);
}
static void Main(string[] args)
{
// Instantiate first hash table
Hashtable ht1 = new Hashtable(1024);
// Add key:value pairs to first HT
ht1.Add("fond", "enamored");
ht1.Add("wrath", "anger");
ht1.Add("diligent", "employed");
ht1.Add("outfit", "garb");
ht1.Add("guide", "usher");
// Instantiate second hash table
Hashtable ht2 = new Hashtable(1024);
// Add other key:value pairs to second HT
ht2.Add("fond", "averse");
ht2.Add("wrath", "delight");
ht2.Add("diligent", "idle");
ht2.Add("guide", "follow");
ht2.Add("flow", "jam");
// Capture list of arrays returned by LeftJoin method
List <string[]> leftJoin = LeftJoin(ht1, ht2);
// Print contents of list of arrays to the console
foreach (var array in leftJoin)
{
for (int i = 0; i < array.Length; i++)
{
Console.Write($"{array[i]} ");
}
Console.WriteLine("");
}
Console.WriteLine("");
}
