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//
// PriorityQueue.cs
//
// Authors:
// Alexander Chebaturkin (chebaturkin@gmail.com)
//
// Copyright (C) 2011 Alexander Chebaturkin
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using System.Collections.Generic;
namespace Mono.CodeContracts.Static.DataStructures {
class PriorityQueue<T> {
private readonly Comparison<T> comparison;
private readonly List<T> values;
public PriorityQueue (Comparison<T> compare)
{
this.comparison = compare;
this.values = new List<T> ();
this.values.Add (default(T)); //fake cell for start from 1
}
public int Count
{
get { return this.values.Count - 1; }
}
public T Peek ()
{
if (Count == 0)
return default(T);
return this.values [1];
}
public T Dequeue ()
{
if (Count == 0)
return default(T);
T res = this.values [1];
this.values [1] = this.values [this.values.Count - 1];
this.values.RemoveAt (this.values.Count - 1);
BubbleDown (1);
return res;
}
public void Enqueue (T item)
{
this.values.Add (item);
BubbleUp (this.values.Count - 1);
}
private void BubbleDown (int i)
{
int l = i << 1;
int r = (i << 1) + 1;
int min = i;
if (l < this.values.Count && this.comparison (this.values [l], this.values [i]) < 0)
min = l;
if (r < this.values.Count && this.comparison (this.values [r], this.values [min]) < 0)
min = r;
if (min != i) {
T tmp = this.values [min];
this.values [min] = this.values [i];
this.values [i] = tmp;
BubbleDown (min);
}
}
private void BubbleUp (int i)
{
int c = i;
while (c/2 != 0 &&
this.comparison (this.values [c >> 1], this.values [c]) > 0) {
T tmp = this.values [c >> 1];
this.values [c >> 1] = this.values [c];
this.values [c] = tmp;
c >>= 1;
}
}
}
}
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