Question

in C++

Design a format for storing graphs in files. This will store your graph into a file with the following requirements:

• The first line will contain the number of Vertices.
• The second line will have a ‘U’ or a ‘D’ to tell the system if it is Undirected or Directed.
• The rest of the lines will be here for each of the edges. Each edge will contain three pieces of information:
  • An integer containing the first Vertex
  • An integer containing the second Vertex
  • An integer containing the weight

You will need to write two functions for your graph, read and write.

• bool read(string filename);
• bool write(string filename);

The file must be human readable (use a txt file please).

Here is a sample input file.

Input.txt

6               # Number of vertices
U               # Undirected graph
0 4 9           # List of Edges
0 2 7
2 3 1
2 1 5
2 5 2

Answer 1

CPP CODE:

#include<iostream>
#include<fstream>
using namespace std;
bool write(string filename)
{
ofstream fout;
fout.open(filename.c_str());
cout<<"Enter number of vertices in graph: ";
int n;
cin>>n;
fout<<n<<endl;
cout<<"Enter U for undirected and D for directed graph: ";
char c;
cin>>c;
fout<<c<<endl;
cout<<"Now add edges by writing first vertex followed by second vertex followed by weight"<<endl;
cout<<"Enter 0 0 0 to end"<<endl;
int graph[n][n];
while(1)
{
int v1,v2,w;
cin>>v1>>v2>>w;
if(v1==0&&v2==0&&w==0)
break;
fout<<v1<<" "<<v2<<" "<<w<<endl;
}
fout.close();
return true;
}
bool read(string filename)
{
ifstream fin;
fin.open(filename.c_str());
cout<<"Reading from file"<<endl;
int n;
fin>>n;
cout<<"Vertices in graph: "<<n<<endl;
char c;
fin>>c;
if(c=='U')
cout<<"Undirected Graph"<<endl;
else
cout<<"Directed Graph"<<endl;
cout<<"V1\tV2\tWeight"<<endl;
int v1,v2,w;
while(fin)
{
fin>>v1>>v2>>w;
cout<<v1<<"\t"<<v2<<"\t"<<w<<endl;
}
}
int main()
{
string filename="graph.txt";
if(write(filename))
cout<<"Graph written in file successfully"<<endl;
if(read(filename))
cout<<"Graph read from file successfully"<<endl;
return 0;
}
Output:

"CAUsers Ashish Shrivastav DesktoplC,C++ Programslgraph2.exe" Enter number of vertices in graph: 6 Enter U for undirected and D for directed graph: U Now add edges by writing first vertex followed by second vertex followed by weight Enter 0 0 0 to end 0 4 9 0 2 7 2 3 1 2 1 5 2 5 2 raph written in file successfullyReading from file ertices in graph: 6 Undirected Graph Weight 4 raph read from file successfully Process returned 0 (0x0) execution time 35.045 s Press any key to continue.

File: graph.txt

graph-Notepad File Edit Format View Help 0 4 9 0 2 7 2 3 1 2 1 5 2 5 2