Create a random graph

createRandomGraph.cpp

#include <iostream>
#include <vector>
#include <iterator>
#include <set>
#include <stdio.h>
#include <stdlib.h>
#include <algorithm>

#define DIRECTED true
#define MULTIPLE_EDGES false
#define MAX_NODES 100
#define MAX_EDGES 100000
#define CONNECTED true
#define MAX_CAPACITY 1000
#define LOOPS_ALLOWED false

struct Edge{
	Edge(){}
	Edge(int from, int to):from(from),to(to){uniqueEdgeGen();}
	int from,to;
	unsigned long long uniqueEdge;

	void uniqueEdgeGen() {
		int a, b;
		if (!DIRECTED) {
			int tmp = std::max(from, to);
			a = std::min(from, to);
			b = tmp;
		} else {
			a = from;
			b = to;
		}
		uniqueEdge = a + b * MAX_NODES;
	}
};

using namespace std;

bool operator<(const Edge& left, const Edge& right)
{
    return left.uniqueEdge < right.uniqueEdge;
}

int main(){
	/* initialize random seed: */
	srand ( time(NULL) );

	/* generate basic graph values */
	unsigned int nodes = rand() % MAX_NODES;
	unsigned int edges = rand() % MAX_EDGES;

	while (!MULTIPLE_EDGES && (edges > (nodes*nodes + nodes) / 2)) {
		edges = rand() % MAX_EDGES;
	}
	
	cout << nodes << " " << edges << endl;

	if (CONNECTED && DIRECTED) {
		if(!MULTIPLE_EDGES) {
			set<Edge> edgeList;
			set<int> visitedSet;
			vector<int> visitedVector;

			visitedSet.insert(0);
			visitedVector.push_back(0);

			while(edgeList.size() < edges) {
				int from = visitedVector[rand() % visitedVector.size()];
				int to = rand() % nodes;
				while (!LOOPS_ALLOWED && from == to) {
					to = rand() % nodes;
				} 
				Edge e = Edge(from, to);
				bool is_in = visitedSet.find(to) != visitedSet.end();
				if(!is_in) {
					visitedVector.push_back(to);
					visitedSet.insert(to);
				}
				edgeList.insert(e);
			}

			/* print them */
			set<Edge>::iterator myIt;
			for(myIt=edgeList.begin(); myIt != edgeList.end(); myIt++){
				cout  << (*myIt).to << " " << (*myIt).from;
				if (MAX_CAPACITY > 0) {
					cout << " " << rand() % MAX_CAPACITY;
				}
				cout << endl;
			}
		}
	} else if (DIRECTED) {
		/* generate edges */
		if(MULTIPLE_EDGES) {
			vector<Edge> edgeList;
			for (unsigned int j = 0; j < edges; j++) {
				int from = rand() % nodes;
				int to = rand() % nodes;
				edgeList.push_back(Edge(from, to));
			}
			/* print them */
			vector<Edge>::iterator myIt;
			for(myIt=edgeList.begin(); myIt != edgeList.end(); myIt++){
				cout << (*myIt).from << " " << (*myIt).to;
				if (MAX_CAPACITY > 0) {
					cout << " " << rand() % MAX_CAPACITY;
				}
				cout << endl;
			}
		} else {
			set<Edge> edgeList;
			while(edgeList.size() < edges) {
				int from = rand() % nodes;
				int to = rand() % nodes;
				Edge e = Edge(from, to);
				edgeList.insert(e);
			}

			/* print them */
			set<Edge>::iterator myIt;
			for(myIt=edgeList.begin(); myIt != edgeList.end(); myIt++){
				cout << (*myIt).from << " " << (*myIt).to;
				if (MAX_CAPACITY > 0) {
					cout << " " << rand() % MAX_CAPACITY;
				}
				cout << endl;
			}
		}
	}

    return 0;
}