Делал индексную очередь с приоритетами, понадобилось реализовывать интерфейс IEnumerable. Получилось так
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class IndexMaxPQ<Key> : IEnumerable<Key> { } |
Понадобилось реализовать 2 следующих метода
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public IEnumerator<Key> GetEnumerator() { return new HeapIterator<Key>(comparer, Size(), n, keys); } IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); } |
В контексте логики класса был написан другой класс HeapIterator
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private class HeapIterator<Key> : IEnumerator<Key> { public Key[] Keys { get; set; } // // store items at indices 1 to n, 0 not use.. public int Size { get; set; } public int N { get; set; } public Comparer<Key> Comparer { get; set; } // private int position = -1; private MaxPQ<Key> copy; public HeapIterator() { if (Comparer == null) copy = new MaxPQ<Key>(Size); else copy = new MaxPQ<Key>(Size, Comparer); for (int i = 0; i < N; N++) copy.Insert(Keys[i]); } public HeapIterator(Comparer<Key> Comparer, int Size, int N, Key[] keys) { this.Comparer = Comparer; this.Size = Size; this.N = N; this.Keys = keys; if (Comparer == null) copy = new MaxPQ<Key>(Size); else copy = new MaxPQ<Key>(Size, Comparer); for (int i = 0; i <= N; i++) copy.Insert(this.Keys[i]); } public bool HasNext() { return !copy.IsEmpty(); } public void Remove() { throw new ArgumentException("error"); } public Key Next() { if (!HasNext()) throw new ArgumentException("error"); return copy.DelMax(); } public void Dispose() { //throw new NotImplementedException(); } public bool MoveNext() { position++; //return !copy.IsEmpty(); return position < copy.Size(); } public void Reset() { position = -1; } // object IEnumerator.Current { get { return Current; } } public Key Current { get { try { // return PQ[position]; return Keys[position]; // << Возвращаем ключики... } catch (IndexOutOfRangeException) { throw new InvalidOperationException(); } } } } |
Все вместе это выглядит так
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using System; using System.Collections; using System.Collections.Generic; using System.Diagnostics; using System.Linq; using System.Text; using System.Threading.Tasks; namespace PriorityQueues { class IndexMaxPQ<Key> : IEnumerable<Key> //Maximum-oriented indexed PQ implementation using a binary heap. { private int n; // number of elements on PQ private int[] pq; // binary heap using 1-based indexing private int[] qp; // inverse of pq - qp[pq[i]] = pq[qp[i]] = i private Key[] keys; // keys[i] = priority of i private Comparer<Key> comparer; // Initializes an empty indexed priority queue with indices between 0 and maxN-1 public IndexMaxPQ(int maxN, Comparer<Key> comparer) { if (maxN < 0) throw new ArgumentException(); n = 0; keys = new Key[maxN + 1]; // make this of length maxN?? pq = new int[maxN + 1]; qp = new int[maxN + 1]; // make this of length maxN?? for (int i = 0; i <= maxN; i++) qp[i] = -1; this.comparer = comparer; } // IsEmpty() public bool IsEmpty() { return n == 0; } // Contains public bool Contains(int i) { return qp[i] != -1; } // Size public int Size() { return n; } // public int MaxIndex() { if (n == 0) throw new ArgumentException("Priority queue underflow"); return pq[1]; } public Key MaxKey() { if (n == 0) throw new ArgumentException("Priority queue underflow"); return keys[pq[1]]; } // Removes a maximum key and returns its associated index. public void DelMax(out int index, out Key key) { if (n == 0) throw new ArgumentException("Priority queue underflow"); int min = pq[1]; key = keys[min]; index = min; Exch(1, n--); Sink(1); Debug.Assert(pq[n + 1] == min); qp[min] = -1; // delete keys[min] = default(Key); // to help with garbage collection pq[n + 1] = -1; // not needed //return min; } // Associate key with index i public void Insert(int i, Key key) { if (Contains(i)) throw new ArgumentException("index is already in the priority queue"); n++; qp[i] = n; pq[n] = i; keys[i] = key; Swim(n); } // public Key KeyOf(int i) { if (!Contains(i)) throw new ArgumentException("index is not in the priority queue"); else return keys[i]; } // public void ChangeKey(int i, Key key) { if (!Contains(i)) throw new ArgumentException("index is not in the priority queue"); keys[i] = key; Swim(qp[i]); Sink(qp[i]); } // Increase the key associated with index {@code i} to the specified value. public void IncreaseKey(int i, Key key) { if (!Contains(i)) throw new ArgumentException("index is not in the priority queue"); //if (keys[i].compareTo(key) >= 0) if (comparer.Compare(keys[i], key) < 0) throw new ArgumentException("Calling increaseKey() with given argument would not strictly increase the key"); keys[i] = key; Swim(qp[i]); } // Decrease the key associated with index {@code i} to the specified value. public void DecreaseKey(int i, Key key) { if (!Contains(i)) throw new ArgumentException("index is not in the priority queue"); if (comparer.Compare(keys[i], key) > 0) throw new ArgumentException("Calling decreaseKey() with given argument would not strictly decrease the key"); keys[i] = key; Sink(qp[i]); } // Remove the key on the priority queue associated with index public void Delete(int i) { if (!Contains(i)) throw new ArgumentException("index is not in the priority queue"); int index = qp[i]; Exch(index, n--); Swim(index); Sink(index); keys[i] = default(Key); qp[i] = -1; } /*************************************************************************** * General helper functions. ***************************************************************************/ private bool Less(int i, int j) { // return keys[pq[i]].CompareTo(keys[pq[j]]) < 0; return comparer.Compare(keys[pq[i]], keys[pq[j]]) < 0; } private void Exch(int i, int j) { int swap = pq[i]; pq[i] = pq[j]; pq[j] = swap; qp[pq[i]] = i; qp[pq[j]] = j; } /*************************************************************************** * Heap helper functions. ***************************************************************************/ private void Swim(int k) { while (k > 1 && Less(k / 2, k)) { Exch(k, k / 2); k = k / 2; } } private void Sink(int k) { while (2 * k <= n) { int j = 2 * k; if (j < n && Less(j, j + 1)) j++; if (!Less(k, j)) break; Exch(k, j); k = j; } } /* public int CompareTo(Key other) { throw new NotImplementedException(); } */ public IEnumerator<Key> GetEnumerator() { return new HeapIterator<Key>(comparer, Size(), n, keys); } IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); } private class HeapIterator<Key> : IEnumerator<Key> { public Key[] Keys { get; set; } // // store items at indices 1 to n, 0 not use.. public int Size { get; set; } public int N { get; set; } public Comparer<Key> Comparer { get; set; } // private int position = -1; private MaxPQ<Key> copy; public HeapIterator() { if (Comparer == null) copy = new MaxPQ<Key>(Size); else copy = new MaxPQ<Key>(Size, Comparer); for (int i = 0; i < N; N++) copy.Insert(Keys[i]); } public HeapIterator(Comparer<Key> Comparer, int Size, int N, Key[] keys) { this.Comparer = Comparer; this.Size = Size; this.N = N; this.Keys = keys; if (Comparer == null) copy = new MaxPQ<Key>(Size); else copy = new MaxPQ<Key>(Size, Comparer); for (int i = 0; i <= N; i++) copy.Insert(this.Keys[i]); } public bool HasNext() { return !copy.IsEmpty(); } public void Remove() { throw new ArgumentException("error"); } public Key Next() { if (!HasNext()) throw new ArgumentException("error"); return copy.DelMax(); } public void Dispose() { //throw new NotImplementedException(); } public bool MoveNext() { position++; //return !copy.IsEmpty(); return position < copy.Size(); } public void Reset() { position = -1; } // object IEnumerator.Current { get { return Current; } } public Key Current { get { try { // return PQ[position]; return Keys[position]; } catch (IndexOutOfRangeException) { throw new InvalidOperationException(); } } } } } } |