Indexed Priority Queue (C# / Unity)
A Generic priority Queue with random access to its elements. I have found this to be an excellent data structure for use within A* search algorithms.
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using System; using UnityEngine.Assertions; namespace Gemini { public sealed class IndexedPriorityQueue { #region public public int Count { get { return m_count; } } public T this[int index] { get { Assert.IsTrue( index < m_objects.Length && index >= 0, string.Format( "IndexedPriorityQueue.[]: Index '{0}' out of range", index ) ); return m_objects[index]; } set { Assert.IsTrue( index < m_objects.Length && index >= 0, string.Format( "IndexedPriorityQueue.[]: Index '{0}' out of range", index ) ); Set( index, value ); } } public IndexedPriorityQueue( int maxSize ) { Resize( maxSize ); } /// /// Inserts a new value with the given index /// /// index to insert at /// value to insert public void Insert( int index, T value ) { Assert.IsTrue( index < m_objects.Length && index >= 0, string.Format( "IndexedPriorityQueue.Insert: Index '{0}' out of range", index ) ); ++m_count; // add object m_objects[index] = value; // add to heap m_heapInverse[index] = m_count; m_heap[m_count] = index; // update heap SortHeapUpward( m_count ); } /// /// Gets the top element of the queue /// /// public T Top() { // top of heap [first element is 1, not 0] return m_objects[m_heap[1]]; } /// /// Removes the top element from the queue /// /// public T Pop() { Assert.IsTrue( m_count > 0, "IndexedPriorityQueue.Pop: Queue is empty" ); if ( m_count == 0 ) { return default( T ); } // swap front to back for removal Swap( 1, m_count-- ); // re-sort heap SortHeapDownward( 1 ); // return popped object return m_objects[m_heap[m_count + 1]]; } /// /// Updates the value at the given index. Note that this function is not /// as efficient as the DecreaseIndex/IncreaseIndex methods, but is /// best when the value at the index is not known /// /// index of the value to set /// new value public void Set( int index, T obj ) { if ( obj.CompareTo( m_objects[index] ) <= 0 ) { DecreaseIndex( index, obj ); } else { IncreaseIndex( index, obj ); } } /// /// Decrease the value at the current index /// /// index to decrease value of /// new value public void DecreaseIndex( int index, T obj ) { Assert.IsTrue( index < m_objects.Length && index >= 0, string.Format( "IndexedPriorityQueue.DecreaseIndex: Index '{0}' out of range", index ) ); Assert.IsTrue( obj.CompareTo( m_objects[index] ) <= 0, string.Format( "IndexedPriorityQueue.DecreaseIndex: object '{0}' isn't less than current value '{1}'", obj, m_objects[index] ) ); m_objects[index] = obj; SortUpward( index ); } /// /// Increase the value at the current index /// /// index to increase value of /// new value public void IncreaseIndex( int index, T obj ) { Assert.IsTrue( index < m_objects.Length && index >= 0, string.Format( "IndexedPriorityQueue.DecreaseIndex: Index '{0}' out of range", index ) ); Assert.IsTrue( obj.CompareTo( m_objects[index] ) >= 0, string.Format( "IndexedPriorityQueue.DecreaseIndex: object '{0}' isn't greater than current value '{1}'", obj, m_objects[index] ) ); m_objects[index] = obj; SortDownward( index ); } public void Clear() { m_count = 0; } /// /// Set the maximum capacity of the queue /// /// new maximum capacity public void Resize( int maxSize ) { Assert.IsTrue( maxSize >= 0, string.Format( "IndexedPriorityQueue.Resize: Invalid size '{0}'", maxSize ) ); m_objects = new T[maxSize]; m_heap = new int[maxSize + 1]; m_heapInverse = new int[maxSize]; m_count = 0; } #endregion // public #region private private T[] m_objects; private int[] m_heap; private int[] m_heapInverse; private int m_count; private void SortUpward( int index ) { SortHeapUpward( m_heapInverse[index] ); } private void SortDownward( int index ) { SortHeapDownward( m_heapInverse[index] ); } private void SortHeapUpward( int heapIndex ) { // move toward top if better than parent while ( heapIndex > 1 && m_objects[m_heap[heapIndex]].CompareTo( m_objects[m_heap[Parent( heapIndex )]] ) < 0 ) { // swap this node with its parent Swap( heapIndex, Parent( heapIndex ) ); // reset iterator to be at parents old position // (child's new position) heapIndex = Parent( heapIndex ); } } private void SortHeapDownward( int heapIndex ) { // move node downward if less than children while ( FirstChild( heapIndex ) <= m_count ) { int child = FirstChild( heapIndex ); // find smallest of two children (if 2 exist) if ( child < m_count && m_objects[m_heap[child + 1]].CompareTo( m_objects[m_heap[child]] ) < 0 ) { ++child; } // swap with child if less if ( m_objects[m_heap[child]].CompareTo( m_objects[m_heap[heapIndex]] ) < 0 ) { Swap( child, heapIndex ); heapIndex = child; } // no swap necessary else { break; } } } private void Swap( int i, int j ) { // swap elements in heap int temp = m_heap[i]; m_heap[i] = m_heap[j]; m_heap[j] = temp; // reset inverses m_heapInverse[m_heap[i]] = i; m_heapInverse[m_heap[j]] = j; } private int Parent( int heapIndex ) { return ( heapIndex / 2 ); } private int FirstChild( int heapIndex ) { return ( heapIndex * 2 ); } private int SecondChild( int heapIndex ) { return ( heapIndex * 2 + 1 ); } #endregion // private } } |