117 lines
4.1 KiB
C#
117 lines
4.1 KiB
C#
/*
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* Yet Another Tiger Compiler (YATC)
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*
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* Copyright 2014 Damian Valdés Santiago, Juan Carlos Pujol Mainegra
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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*/
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using System.Collections.Generic;
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using System.Linq;
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namespace YATC.ASTNodes
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{
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internal class Node<T>
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{
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public enum ColorCode
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{
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White = 0,
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Unvisited = 0,
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Black = 1,
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Done = 1,
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Gray = 2,
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StillNotDone = 2
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}
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public ColorCode Color { get; private set; }
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public Node<T> Parent { get; private set; }
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public readonly T Value;
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public Node(T value)
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{
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this.Value = value;
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}
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private readonly LinkedList<Node<T>> _pred = new LinkedList<Node<T>>();
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private readonly LinkedList<Node<T>> _succ = new LinkedList<Node<T>>();
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public IEnumerable<Node<T>> Pred { get { return _pred; } }
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public IEnumerable<Node<T>> Succ { get { return _succ; } }
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public IEnumerable<Node<T>> Adj { get { return _pred.Concat(_succ); } }
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public void AddSucc(Node<T> node) { _succ.AddLast(node); }
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public void AddPred(Node<T> node) { _pred.AddLast(node); }
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private static Node<T> DFS(IEnumerable<Node<T>> nodes, bool checkCycles, out LinkedList<Node<T>> linkedList)
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{
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int time = 0;
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linkedList = new LinkedList<Node<T>>();
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foreach (var node in nodes.Where(node => node.Color == ColorCode.White))
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{
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var cycleEnd = node.Visit(ref time, checkCycles, linkedList);
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if (cycleEnd != null)
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return cycleEnd;
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}
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return null;
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}
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private Node<T> Visit(ref int time, bool checkCycles, LinkedList<Node<T>> topologicalSort)
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{
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this.Color = ColorCode.Gray;
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foreach (var node in this.Succ)
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{
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// by the Proof of Theorem 22.12, page 614, (u,v) is a back edge iff v is Gray
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// from Cormen et al. - Introduction To Algorithms, 3rd edition
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if (node.Color == ColorCode.Gray && checkCycles)
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return this;
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if (node.Color == ColorCode.White)
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{
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node.Parent = this;
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var cycleEnd = node.Visit(ref time, checkCycles, topologicalSort);
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if (cycleEnd != null)
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return cycleEnd;
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}
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}
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this.Color = ColorCode.Black;
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topologicalSort.AddFirst(this);
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return null;
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}
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public static Node<T> TopologicalSort(IEnumerable<Node<T>> nodes, out LinkedList<Node<T>> linkedList)
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{
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return DFS(nodes, true, out linkedList);
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}
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public class NodeValueEqualityComparer : IEqualityComparer<Node<T>>
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{
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public bool Equals(Node<T> x, Node<T> y)
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{
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return x.Value.Equals(y.Value);
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}
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public int GetHashCode(Node<T> obj)
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{
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return obj.Value.GetHashCode();
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}
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}
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}
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} |