Edge list

Edge list is a list of edges with nodes. Essentially, it s a list of all possible connections. it is represented by an array of arrays. Edge list is mostly used when a graph is undirected.

const edges = [  
  ["i", "j"],  
  ["k", "i"],  
  ["m", "k"],  
  ["k", "l"],  
  ["o", "n"],  
];  

Transformation of Edge list to Adjacency list

Edge list, by itself is not very useful if you want to traverse through a graph. To be able to do that, you have transform the edge list to adjacency list. Below is an example of how to do it.

const edges = [  
  ["i", "j"],  
  ["k", "i"],  
  ["m", "k"],  
  ["k", "l"],  
  ["o", "n"],  
];  
  
function buildGraph(edges) {  
  const graph = {};  
  
  edges.forEach((edge) => {  
    const [a, b] = edge;  
    if (!graph[a]) graph[a] = [];  
    if (!graph[b]) graph[b] = [];  
    graph[a].push(b);  
    graph[b].push(a);  
  });  
  
  return graph;  
}  
  
// Output:  
/*  
{  
  i: [ 'j', 'k' ],  
  j: [ 'i' ],  
  k: [ 'i', 'm', 'l' ],  
  m: [ 'k' ],  
  l: [ 'k' ],  
  o: [ 'n' ],  
  n: [ 'o' ]  
}  
*/