/// <summary>
/// Merges two priority queues
/// </summary>
/// <param name="pq1">first priority queue</param>
/// <param name="pq2">second priority queue</param>
/// <returns>resultant priority queue</returns>
/// <remarks>
/// source priority queues must have equal comparers,
/// otherwise <see cref="InvalidOperationException"/> will be thrown
/// </remarks>
public static MaxPriorityQueue <TPriority, TValue> MergeQueues(MaxPriorityQueue <TPriority, TValue> pq1, MaxPriorityQueue <TPriority, TValue> pq2)
{
if (pq1 == null || pq2 == null)
{
throw new ArgumentNullException();
}
if (pq1._comparer != pq2._comparer)
{
throw new InvalidOperationException("Priority queues to be merged must have equal comparers");
}
return(MergeQueues(pq1, pq2, pq1._comparer));
}
/// <summary>
/// Merges two priority queues and sets specified comparer for resultant priority queue
/// </summary>
/// <param name="pq1">first priority queue</param>
/// <param name="pq2">second priority queue</param>
/// <param name="comparer">comparer for resultant priority queue</param>
/// <returns>resultant priority queue</returns>
public static MaxPriorityQueue <TPriority, TValue> MergeQueues(MaxPriorityQueue <TPriority, TValue> pq1, MaxPriorityQueue <TPriority, TValue> pq2, IComparer <TPriority> comparer)
{
if (pq1 == null || pq2 == null || comparer == null)
{
throw new ArgumentNullException();
}
// merge data
MaxPriorityQueue <TPriority, TValue> result = new MaxPriorityQueue <TPriority, TValue>(pq1.Count + pq2.Count, pq1._comparer);
result._baseHeap.AddRange(pq1._baseHeap);
result._baseHeap.AddRange(pq2._baseHeap);
// heapify data
for (int pos = result._baseHeap.Count / 2 - 1; pos >= 0; pos--)
{
result.HeapifyFromBeginningToEnd(pos);
}
return(result);
}
public static void Execute(string inputFile)
{
MaxPriorityQueue <int, int> hLow = new MaxPriorityQueue <int, int>();
PriorityQueue <int, int> hHigh = new PriorityQueue <int, int>();
string[] lines = File.ReadAllLines(inputFile);
int medianSum = 0;
//hHigh.Enqueue(1, 0);
//hHigh.Enqueue(2, 0);
//hHigh.Enqueue(3, 0);
//hHigh.Enqueue(4, 0);
//hLow.Enqueue(1, 0);
//hLow.Enqueue(2, 0);
//hLow.Enqueue(3, 0);
//hLow.Enqueue(4, 0);
// Maintain invariant ~ i/2 smallest(or largest) elements in hLow(or hHigh)
/* If incoming i > hLow, enqueue in hHigh and vice-versa.
* if count(hLow) > count(hHigh), Dequeue hLow to hHigh and vice-versa.
*/
foreach (string line in lines)
{
int x = Int32.Parse(line);
// If hLow is empty, enqueue x
if (hLow.Count == 0)
{
hLow.Enqueue(x, 0);
medianSum += hLow.Peek().Key;
continue;
}
if (x > hLow.Peek().Key)
{
hHigh.Enqueue(x, 0);
}
else
{
hLow.Enqueue(x, 0);
}
// Balance heaps
if (hLow.Count > hHigh.Count)
{
if (hLow.Count - hHigh.Count > 1)
{
hHigh.Enqueue(hLow.Dequeue().Key, 0);
}
}
else
{
if (hHigh.Count - hLow.Count > 1)
{
hLow.Enqueue(hHigh.Dequeue().Key, 0);
}
}
medianSum += ((hLow.Count + hHigh.Count) % 2 == 0) ? hLow.Peek().Key :
(hLow.Count > hHigh.Count) ? hLow.Peek().Key : hHigh.Peek().Key;
}
}
