Question

Write a  Python or C++ program that takes as input a directed graph and returns a copy of the graph with all edges reversed. You can only assume that you have access to the sequence of nodes and the sequence of edges of the graph. Generate a random graph and test your program on it.

Answer 1

Code:

#include<bits/stdc++.h>
using namespace std;
int vertices = 4 , edges =6;
vector<int>original[4];
vector<int>reversed[4];

// method to store the reversed edges
void reverse_edges(){
for(int i=0;i<vertices;i++){
for(int j=0;j<original[i].size();j++){
int k=original[i][j];
reversed[k].push_back(i);
}
}
}

int main(){
  
// take edges as input from user
  
for(int i=0;i<edges;i++){
int u,v;
cin>>u>>v;
original[u].push_back(v);
}
  
// print the original edges
cout<<"Original edges are as follows : \n";
  
for(int i=0;i<vertices;i++){
for(int j=0;j<original[i].size();j++){
cout<<i<<" -> "<<original[i][j]<<"\n";

}
}
reverse_edges();
  
// print the reversed edges
cout<<"Reversed edges are as follows : \n";
  
for(int i=0;i<vertices;i++){
for(int j=0;j<reversed[i].size();j++){
cout<<i<<" -> "<<reversed[i][j]<<"\n";

}
}
}

Screenshots:

#include<bits/stdc++.h> using namespace std; int vertices = 4 , edges =6; vector int>original[4]; vector<int>reversed[4]; // method to store the reversed edges void reverse_edges() { for(int i=0;i<vertices; i++) { for(int j=0; j<original[i].size(); j++){ int k=original[i][j]; reversed[k].push_back(i); TO int main() { // take edges as input from user for(int i=0;i<edges; i++) { int u,v; cin>>u>>v; original[u].push_back(v);

// print the original edges cout<<"Original edges are as follows : \n"; for(int i=0;i<vertices; i++) { for(int j=0; j<original[i].size(); j++){ cout<<i<<" -> "<<original[i][j]<<"\n"; reverse_edges(); // print the reversed edges cout<<"Reversed edges are as follows: \n"; for(int i=0; i<vertices; i++) { for(int j=0; j<reversed[i].size(); j++){ cout<<i<<" -> "<<reversed[i][j]<<"\n";

Output:

Original edges are as follows: -> 1 O-> 2 0 -> 3 1 -> 3 1 -> 2 2 -> 3 w nown

Reversed edges are as follows: 1 -> o 2 -> o 2 -> 1 3 -> 0 3 -> 1 3 -> 2 wwwNN