Examples:

Input: adjList[] = {{0 –> 1 –> 3}, {1 –> 2}, {2 –> 3}}
Output:
0 1 0 1
0 0 1 0
0 0 0 1
0 0 0 0

Input: adjList[] = {{0 –> 1 –> 4}, {1 –> 0 –> 2 –> 3 –> 4}, {2 –> 1 –> 3}, {3 –> 1 –> 2 –> 4}, {4 –> 0 –> 1 –> 3}}
Output:
0 1 0 0 1
1 0 1 1 1
0 1 0 1 0
0 1 1 0 1
1 1 0 1 0

Adjacency List: An array of lists is used. The size of the array is equal to the number of vertices. Let the array be an array[]. An entry array[i] represents the list of vertices adjacent to the ith Vertex.

Adjacency Matrix: Adjacency Matrix is a 2D array of size V x V where V is the number of vertices in a graph. Let the 2D array be adj[][], a slot adj[i][j] = 1 indicates that there is an edge from vertex i to vertex j.

• Initialize a matrix with 0s.
• Iterate over the vertices in the adjacency list
• For every jth vertex in the adjacency list, traverse its edges.
• For each vertex i with which the jth vertex has an edge, set mat[i][j] = 1.

Below is the implementation of the above approach:

## C++

 `// C++ Program to implement ` `// the above approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to insert vertices to adjacency list ` `void` `insert(vector<``int``> adj[], ``int` `u, ``int` `v) ` `{ ` `    ``// Insert a vertex v to vertex u ` `    ``adj[u].push_back(v); ` `    ``return``; ` `} ` ` `  `// Function to display adjacency list ` `void` `printList(vector<``int``> adj[], ``int` `V) ` `{ ` `    ``for` `(``int` `i = 0; i < V; i++) { ` `        ``cout << i; ` `        ``for` `(``auto` `j : adj[i]) ` `            ``cout << ``" --> "` `<< j; ` `        ``cout << endl; ` `    ``} ` `    ``cout << endl; ` `} ` ` `  `// Function to convert adjacency ` `// list to adjacency matrix ` `vector > convert(vector<``int``> adj[], ` `                             ``int` `V) ` `{ ` `    ``// Initialize a matrix ` `    ``vector > matrix(V, ` `                                ``vector<``int``>(V, 0)); ` ` `  `    ``for` `(``int` `i = 0; i < V; i++) { ` `        ``for` `(``auto` `j : adj[i]) ` `            ``matrix[i][j] = 1; ` `    ``} ` `    ``return` `matrix; ` `} ` ` `  `// Function to display adjacency matrix ` `void` `printMatrix(vector > adj, ``int` `V) ` `{ ` `    ``for` `(``int` `i = 0; i < V; i++) { ` `        ``for` `(``int` `j = 0; j < V; j++) { ` `            ``cout << adj[i][j] << ``"   "``; ` `        ``} ` `        ``cout << endl; ` `    ``} ` `    ``cout << endl; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `V = 5; ` ` `  `    ``vector<``int``> adjList[V]; ` ` `  `    ``// Inserting edges ` `    ``insert(adjList, 0, 1); ` `    ``insert(adjList, 0, 4); ` `    ``insert(adjList, 1, 0); ` `    ``insert(adjList, 1, 2); ` `    ``insert(adjList, 1, 3); ` `    ``insert(adjList, 1, 4); ` `    ``insert(adjList, 2, 1); ` `    ``insert(adjList, 2, 3); ` `    ``insert(adjList, 3, 1); ` `    ``insert(adjList, 3, 2); ` `    ``insert(adjList, 3, 4); ` `    ``insert(adjList, 4, 0); ` `    ``insert(adjList, 4, 1); ` `    ``insert(adjList, 4, 3); ` ` `  `    ``// Display adjacency list ` `    ``cout << ``"Adjacency List: \n"``; ` `    ``printList(adjList, V); ` ` `  `    ``// Function call which returns ` `    ``// adjacency matrix after conversion ` `    ``vector > adjMatrix ` `        ``= convert(adjList, V); ` ` `  `    ``// Display adjacency matrix ` `    ``cout << ``"Adjacency Matrix: \n"``; ` `    ``printMatrix(adjMatrix, V); ` ` `  `    ``return` `0; ` `} `

Output:

```Adjacency List:
0 --> 1 --> 4
1 --> 0 --> 2 --> 3 --> 4
2 --> 1 --> 3
3 --> 1 --> 2 --> 4
4 --> 0 --> 1 --> 3

0   1   0   0   1
1   0   1   1   1
0   1   0   1   0
0   1   1   0   1
1   1   0   1   0
```

Time Complexity: O(N*M)
Auxiliary Space: O(N2)

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