edges-to-adjacency-list/e2a.js

Convert a list of edges to an adjacency list

"use strict"

module.exports = edgeToAdjacency

var uniq = require("uniq")

function edgeToAdjacency(edges, numVertices) {
  var numEdges = edges.length
  if(typeof numVertices !== "number") {
    numVertices = 0
    for(var i=0; i<numEdges; ++i) {
      var e = edges[i]
      numVertices = Math.max(numVertices, e[0], e[1])
    }
    numVertices = (numVertices|0) + 1
  }
  numVertices = numVertices|0
  var adj = new Array(numVertices)
  for(var i=0; i<numVertices; ++i) {
    adj[i] = []
  }
  for(var i=0; i<numEdges; ++i) {
    var e = edges[i]
    adj[e[0]].push(e[1])
    adj[e[1]].push(e[0])
  }
  for(var j=0; j<numVertices; ++j) {
    uniq(adj[j], function(a, b) {
      return a - b
    })
  }
  return adj
}