Memory leak in Depth First Search Algorithm on Graphs - c++

Question

I was doing a course on Coursera where they asked to implement DFS to see if two vertices of a graph are connected. I came up with the code and it gives the correct output on my laptop but it gives incorrect output on their grader. I've been breaking my head for days on this problem and have absolutely no idea where I've gone wrong. The code is as follows:
#include<iostream>
#include<vector>
using namespace std;
class Graph
{
public:
vector<int> adj; //adjacency list
void add(int a)
{
adj.push_back(a);
}
void DFS(bool visited[],int n,Graph G[],int v)
{
for(int i=0;i<G[v].adj.size();i++)
{
int vert=G[v].adj[i];
if(visited[vert]==false)
{
visited[vert]=true;
DFS(visited,n,G,vert);
}
}
}
};
int main()
{
int n,m;
cin>>n>>m;//No. of vertices,number of edges
bool visited[n];
for(int i=0;i<n;i++)
visited[n]=false;
Graph G[n];
for(int i=0;i<m;i++)
{
int u,v;
cin>>u>>v; //The vertices joined by two edges
G[u-1].add(v-1);
G[v-1].add(u-1);
}
int k,l;
cin>>k>>l; //The vertices to be checked if they are connected
G[k-1].DFS(visited,n,G,k-1);
if(visited[l-1]==true)
cout<<1;
else
cout<<0;
}
Grader Output:
Failed case #2/16: (Wrong answer)
Input:
4 2
1 2
3 2
1 4
Your output:
1
Correct output:
0
(Time used: 0.00/1.00, memory used: 7839744/536870912.)
If I run the above case in my laptop, it gives the output as 0, the expected answer. I asked the question on the forum and they say that there is some memory leak which I can't identify. Please help.

Answer 1

If you're writing a Graph class, then you should really encapsulate all functionality inside that class. You're not supposed to overwhelm the main function. It makes your code convoluted. Plus you don't have to pass around a lot things in case of a function call. Avoid using using namespace std; as it will lead to namespace collision. To avoid writing std::cout or std::cin, consider using std::cout and using std::cin. I refactored your code and now it gives correct output:
#include <iostream>
#include <cstring>
#include <vector>
using std::cout;
using std::cin;
class Graph
{
public:
static constexpr int MAXN = 100;
std::vector <int> adj[MAXN + 1]; //adjacency list
int visited[Graph::MAXN + 1]; // for 1 based indexing
Graph(){
for(int i = 0 ; i <= MAXN ; ++i) adj[i].clear();
memset(visited, 0, sizeof(visited));
}
void addEdge(bool isDirected, int u, int v)
{
adj[u].push_back(v);
if(!isDirected) adj[v].push_back(u);
}
void takeInput(bool isDirected, int nodes, int edges){
for(int i = 0 ; i < edges ; i++){
int u,v; cin >> u >> v;
addEdge(isDirected, u, v);
}
}
void DFS(int source)
{
visited[source] = 1;
for(int i = 0 ; i < adj[source].size() ; ++i){
int adjNode = adj[source][i];
if(visited[adjNode] == 0){
DFS(adjNode);
}
}
}
bool isConnected(int source, int destination){
DFS(source - 1);
return visited[destination - 1];
}
};
int main()
{
int nodes, edges;
cin >> nodes >> edges;//No. of vertices,number of edges
Graph g;
g.takeInput(false, nodes, edges);
int source, destination;
cin >> source >> destination; //The vertices to be checked if they are connected
cout << g.isConnected(source, destination) << '\n';
return 0;
}