Print Adjacency List [TC: O(V+E); SC: O(1)]

print-adj-list.cpp

// Problem Link: https://practice.geeksforgeeks.org/problems/print-adjacency-list-1587115620/1/

// The Graph structure is as folows

// Function to print graph
// adj: array of vectors to represent graph
// V: number of vertices
void printGraph(vector<int> adj[], int V) {
  for(int u = 0; u < V; ++u) {
    if((int)adj[u].size() == 0) cout << u;
    else cout << u << "-> ";
    for(int v = 0; v < (int)adj[u].size(); ++v)
      if(v + 1 == adj[u].size())
        cout << adj[u][v];
      else cout << adj[u][v] << "-> ";
    cout << "\n";
  }
}

void addEdge(vector<int> *adj, int u, int v) {
  adj[u].push_back(v);
  adj[v].push_back(u);
}

int main() {
  int t;  cin >> t;
  while(t--) {
    int vertices, edges, u, v; 
    cin >> vertices >> edges;
    
    // Initialize the graph: G(V, E) -> represented as G[u][v]
    vector<int> G[vertices];
    for(int i = 0; i < edges; ++i) {
      cin >> u >> v;
      addEdge(G, u, v);
    }
    
    printGraph(G, vertices) << "\n";
  }
  return 0;
}

Problem Link