Greedy-Graph-Coloring/graph-coloring.cpp at master · hanabhp/Greedy-Graph-Coloring · GitHub

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/*
 author: Hana B Pasandi (barahoueipash@vcu.edu)
 file: graph-coloring.cpp
 This is a programming assignment for CMSC501
 */

#include <iostream>
#include <list>
#include <string>
#include <sstream>
#include <algorithm>
#include <iterator>
#include <vector>
# include <fstream>


using namespace std;

class Graph
{
	int V;
	list<int> *adj;
public:

	Graph(int V) { this->V = V; adj = new list<int>[V]; }
	~Graph() { delete[] adj; }


	void addEdge(int v, int w);


	void greedyColoring(vector<int> tokens);
};

void Graph::addEdge(int v, int w)
{
	adj[v].push_back(w);
	adj[w].push_back(v);
}

struct vertexDegree
{
    int v;
    int degree;
};

bool compareByDegree(const vertexDegree& x, const vertexDegree& y)
{
    return x.degree > y.degree;
}

void Graph::greedyColoring(vector<int> tokens)
{
	int maxin = 0;
	int *result = new int[V];

	if (tokens.size() == V){
		for (int j = 0; j <= V; ++j)
			{
				if (tokens[j] >= 0)
					result[j] = tokens[j];
			}
	}

	for (int i = 0; i<V; i++)
	{
		if (result[i] > maxin)
			maxin = result[i];
	}


	int max_degree=0;

	vertexDegree arr[V];
    for (int i = 0; i < V; i++)
    {
        arr[i].v = i;
        arr[i].degree = adj[i].size();

        if(arr[i].degree>=max_degree){
        	max_degree = arr[i].degree;
        }
    }

    cout <<"max degree: "<< max_degree <<endl;


	bool *colored = new bool[V];
	for (int c = 0; c < V; c++)
		colored[c] = false;

	for (int u = 0; u < V; u++)
	{

		list<int>::iterator i;
		for (i = adj[u].begin(); i != adj[u].end(); ++i)
			if (result[*i] != -1)
				colored[result[*i]] = true;


		int c;
		for (c = 0; c < V; c++)
			if (colored[c] == false)
				break;
		if (result[u] <= 0)
			result[u] = c;


		for (i = adj[u].begin(); i != adj[u].end(); ++i)
			if (result[*i] != -1)
				colored[result[*i]] = false;
	}
	int maxout = 0;

	for (int i = 0; i<V; i++)
	{
		if (result[i]+1 > maxout)
			maxout = result[i]+1;
	}


	ofstream myfile2;
	myfile2.open("output.txt");
	myfile2 << abs (maxout-1) << endl;
	cout << "# of colors: "<<(maxout-1)<<endl;


	for (int u = 0; u < V; u++)
		myfile2 << result[u] << "  ";


	myfile2.close();

}


int main(int argc, char *argv[])
{
	ifstream myfile(argv[1]);
	string str;
	if (myfile.is_open()) {

		getline(myfile , str);
		istringstream iss(str);
		vector<int> tokens ((istream_iterator<int>(iss)), istream_iterator<int>());
		int V = tokens[0];
		int M = tokens[1];

		Graph g(V);
		while (getline(myfile, str)) {

			istringstream iss(str);
			vector<int> tokens ((istream_iterator<int>(iss)), istream_iterator<int>());
			int v = tokens[0];
			int w = tokens[1];
			if (tokens.size() == 2)
				g.addEdge(v - 1, w - 1);
			if (tokens.size() < 2 || (tokens.size() > 2 && tokens.size() != V)) {

			}


			if (tokens.size() > 2) {
				g.greedyColoring(tokens);
			}

		}
	}

	else cout << " Unable to open your file";

	return 0;
}