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| class BinaryHeap<T> | |
| { | |
| public T[] Heap { get; } | |
| public int Count { get; private set; } | |
| public IComparer<T> Comparer { get; } | |
| public BinaryHeap(int size, IComparer<T> comparer = null) | |
| { | |
| Heap = new T[size]; | |
| Count = 0; | |
| Comparer = comparer ?? Comparer<T>.Default; | |
| } | |
| public T Peek() | |
| { | |
| if (Count == 0) | |
| throw new Exception("Empty"); | |
| return Heap[0]; | |
| } | |
| public void Push(T value) | |
| { | |
| if (Count == Heap.Length) | |
| throw new Exception("Heap overflow"); | |
| var i = Count++; | |
| Heap[i] = value; | |
| while (i > 0) | |
| { | |
| var parent = (i + 1) / 2 - 1; | |
| if (IsGreater(Heap[i], Heap[parent])) | |
| break; | |
| Swap(i, parent); | |
| i = parent; | |
| } | |
| } | |
| public T Pop() | |
| { | |
| if (Count == 0) | |
| throw new Exception("Empty"); | |
| var v = Heap[0]; | |
| var size = --Count; | |
| Swap(0, size); | |
| var i = 0; | |
| while (i < size - 1) | |
| { | |
| var left = i * 2 + 1; | |
| var right = i * 2 + 2; | |
| int child; | |
| if (right < size && IsGreater(Heap[left], Heap[right])) | |
| child = right; | |
| else if (left < size) | |
| child = left; | |
| else | |
| break; | |
| if (IsGreater(Heap[child], Heap[i])) | |
| break; | |
| Swap(i, child); | |
| i = child; | |
| } | |
| return v; | |
| } | |
| private bool IsGreater(T a, T b) | |
| { | |
| return Comparer.Compare(a, b) > 0; | |
| } | |
| private void Swap(int i1, int i2) | |
| { | |
| var v = Heap[i1]; | |
| Heap[i1] = Heap[i2]; | |
| Heap[i2] = v; | |
| } | |
| } |
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