CompleteBipartiteGraph.cs

Go to the documentation of this file.

#region License
/*This file is part of Satsuma Graph Library
Copyright © 2013 Balázs Szalkai

This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

   1. The origin of this software must not be misrepresented; you must not
   claim that you wrote the original software. If you use this software
   in a product, an acknowledgment in the product documentation would be
   appreciated but is not required.

   2. Altered source versions must be plainly marked as such, and must not be
   misrepresented as being the original software.

   3. This notice may not be removed or altered from any source
   distribution.*/
#endregion

using System;
using System.Collections.Generic;

namespace Satsuma
{
    public sealed class CompleteBipartiteGraph : IGraph
    {
        public enum Color
        {
            Red, 
            Blue
        }

        public int RedNodeCount { get; private set; }
        public int BlueNodeCount { get; private set; }
        public bool Directed { get; private set; }

        public CompleteBipartiteGraph(int redNodeCount, int blueNodeCount, Directedness directedness)
        {
            if (redNodeCount < 0 || blueNodeCount < 0)
                throw new ArgumentException("Invalid node count: " + redNodeCount + ";" + blueNodeCount);
            if ((long)redNodeCount + blueNodeCount > int.MaxValue ||
                (long)redNodeCount * blueNodeCount > int.MaxValue)
                throw new ArgumentException("Too many nodes: " + redNodeCount + ";" + blueNodeCount);

            RedNodeCount = redNodeCount;
            BlueNodeCount = blueNodeCount;
            Directed = (directedness == Directedness.Directed);
        }
        
        public Node GetRedNode(int index)
        {
            return new Node(1L + index);
        }

        public Node GetBlueNode(int index)
        {
            return new Node(1L + RedNodeCount + index);
        }

        public bool IsRed(Node node)
        {
            return node.Id <= RedNodeCount;
        }

        public Arc GetArc(Node u, Node v)
        {
            bool ured = IsRed(u);
            bool vred = IsRed(v);

            if (ured == vred) return Arc.Invalid;
            if (vred)
            {
                var t = u; u = v; v = t;
            }

            int uindex = (int)(u.Id - 1);
            int vindex = (int)(v.Id - RedNodeCount - 1);

            return new Arc(1 + (long)vindex * RedNodeCount + uindex);
        }

        public Node U(Arc arc)
        {
            return new Node(1L + (arc.Id - 1) % RedNodeCount);
        }

        public Node V(Arc arc)
        {
            return new Node(1L + RedNodeCount + (arc.Id - 1) / RedNodeCount);
        }

        public bool IsEdge(Arc arc)
        {
            return !Directed;
        }

        public IEnumerable<Node> Nodes(Color color)
        {
            switch (color)
            {
                case Color.Red:
                    for (int i = 0; i < RedNodeCount; i++)
                        yield return GetRedNode(i);
                    break;

                case Color.Blue:
                    for (int i = 0; i < BlueNodeCount; i++)
                        yield return GetBlueNode(i);
                    break;
            }
        }

        public IEnumerable<Node> Nodes()
        {
            for (int i = 0; i < RedNodeCount; i++)
                yield return GetRedNode(i);
            for (int i = 0; i < BlueNodeCount; i++)
                yield return GetBlueNode(i);
        }

        public IEnumerable<Arc> Arcs(ArcFilter filter = ArcFilter.All)
        {
            if (Directed && filter == ArcFilter.Edge) yield break;

            for (int i = 0; i < RedNodeCount; i++)
                for (int j = 0; j < BlueNodeCount; j++)
                    yield return GetArc(GetRedNode(i), GetBlueNode(j));
        }

        public IEnumerable<Arc> Arcs(Node u, ArcFilter filter = ArcFilter.All)
        {
            bool isRed = IsRed(u);
            if (Directed && (filter == ArcFilter.Edge ||
                (filter == ArcFilter.Forward && !isRed) ||
                (filter == ArcFilter.Backward && isRed))) yield break;

            if (isRed)
            {
                for (int i = 0; i < BlueNodeCount; i++)
                    yield return GetArc(u, GetBlueNode(i));
            }
            else
            {
                for (int i = 0; i < RedNodeCount; i++)
                    yield return GetArc(GetRedNode(i), u);
            }
        }

        public IEnumerable<Arc> Arcs(Node u, Node v, ArcFilter filter = ArcFilter.All)
        {
            Arc arc = GetArc(u, v);
            if (arc != Arc.Invalid && ArcCount(u, filter) > 0) yield return arc;
        }

        public int NodeCount()
        {
            return RedNodeCount + BlueNodeCount;
        }

        public int ArcCount(ArcFilter filter = ArcFilter.All)
        {
            if (Directed && filter == ArcFilter.Edge) return 0;
            return RedNodeCount * BlueNodeCount;
        }

        public int ArcCount(Node u, ArcFilter filter = ArcFilter.All)
        {
            bool isRed = IsRed(u);
            if (Directed && (filter == ArcFilter.Edge ||
                (filter == ArcFilter.Forward && !isRed) ||
                (filter == ArcFilter.Backward && isRed))) return 0;

            return isRed ? BlueNodeCount : RedNodeCount;
        }

        public int ArcCount(Node u, Node v, ArcFilter filter = ArcFilter.All)
        {
            if (IsRed(u) == IsRed(v)) return 0;
            return ArcCount(u, filter) > 0 ? 1 : 0;
        }

        public bool HasNode(Node node)
        {
            return node.Id >= 1 && node.Id <= RedNodeCount + BlueNodeCount;
        }

        public bool HasArc(Arc arc)
        {
            return arc.Id >= 1 && arc.Id <= RedNodeCount * BlueNodeCount;
        }
    }
}