gistfile1.js

var MAX_DEPTH = 3;
 
var findPath = function (source, target, u2f, visitor) { // u2f = user to friend
  source = Graph.userToIndex(source);
  target = Graph.userToIndex(target);
  var dist = []
  var prev = []
  var queue = []
  var seen  = []
 
  dist[source] = 0
  prev[source] = source
  queue[queue.length] = source
  var len = 1;
 
  while (len > 0) {
    var cur = queue.shift() // pop the front element
    --len;
    var d = dist[cur]
 
    if (cur == target) {
      var path = []
      var pos = target
      while (prev[pos] != source) {
        path.unshift({
          user: pos
        });
        pos = prev[pos]
      }
      visitor(source, target, path)
      continue;
      //return d
    }
 
    if (d > MAX_DEPTH)
       return d
 
    var friends = u2f[cur];
    if(!friends) continue;
    
    for (var fi = friends.length; fi--; ) {
      var next = friends[fi];
      if(seen[next]) continue;
      seen[next] = true;
      var nextd = dist[next] ? dist[next] : 987654321 // inf 
      if (d + 1 < nextd) {
         dist[next] = d + 1
         prev[next] = cur
         queue[len] = next
         ++len;
      }
    }
  }
  return dist[target]
}
 
findPath;