C program to implement Adjacency Matrix of a given Graph
Given a undirected Graph of N vertices 1 to N and M edges in form of 2D array arr[][] whose every row consists of two numbers X and Y which denotes that there is a edge between X and Y, the task is to write C program to create Adjacency Matrix of the given Graph.
Examples:
Input: N = 5, M = 4, arr[][] = { { 1, 2 }, { 2, 3 }, { 4, 5 }, { 1, 5 } }
Output:
0 1 0 0 1
1 0 1 0 0
0 1 0 0 0
0 0 0 0 1
1 0 0 1 0Input: N = 3, M = 4, arr[][] = { { 1, 2 }, { 2, 3 }, { 3, 1 }, { 2, 2 } }
Output:
0 1 1
1 1 1
1 1 0
Approach: The idea is to use a square Matrix of size NxN to create Adjacency Matrix. Below are the steps:
- Create a 2D array(say Adj[N+1][N+1]) of size NxN and initialise all value of this matrix to zero.
- For each edge in arr[][](say X and Y), Update value at Adj[X][Y] and Adj[Y][X] to 1, denotes that there is a edge between X and Y.
- Display the Adjacency Matrix after the above operation for all the pairs in arr[][].
Below is the implementation of the above approach:
// C program for the above approach#include <stdio.h> // N vertices and M Edgesint N, M; // Function to create Adjacency Matrixvoid createAdjMatrix(int Adj[][N + 1], int arr[][2]){ // Initialise all value to this // Adjacency list to zero for (int i = 0; i < N + 1; i++) { for (int j = 0; j < N + 1; j++) { Adj[i][j] = 0; } } // Traverse the array of Edges for (int i = 0; i < M; i++) { // Find X and Y of Edges int x = arr[i][0]; int y = arr[i][1]; // Update value to 1 Adj[x][y] = 1; Adj[y][x] = 1; }} // Function to print the created// Adjacency Matrixvoid printAdjMatrix(int Adj[][N + 1]){ // Traverse the Adj[][] for (int i = 1; i < N + 1; i++) { for (int j = 1; j < N + 1; j++) { // Print the value at Adj[i][j] printf("%d ", Adj[i][j]); } printf("\n"); }} // Driver Codeint main(){ // Number of vertices N = 5; // Given Edges int arr[][2] = { { 1, 2 }, { 2, 3 }, { 4, 5 }, { 1, 5 } }; // Number of Edges M = sizeof(arr) / sizeof(arr[0]); // For Adjacency Matrix int Adj[N + 1][N + 1]; // Function call to create // Adjacency Matrix createAdjMatrix(Adj, arr); // Print Adjacency Matrix printAdjMatrix(Adj); return 0;} |
0 1 0 0 1 1 0 1 0 0 0 1 0 0 0 0 0 0 0 1 1 0 0 1 0
Time Complexity: O(N2), where N is the number of vertices in a graph.
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