Force Layout from Adjacency List by mbostock

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<style>

line {
  stroke: #ccc;
  stroke-width: 1.5px;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>

var width = 960,
    height = 500;

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);

var force = d3.layout.force()
    .size([width, height]);

d3.json("graph.json", function(error, graph) {
  if (error) throw error;

  var nodes = d3.values(graph),
      links = d3.merge(nodes.map(function(source) {
        return source.map(function(target) {
          return {source: source, target: graph[target]};
        });
      }));

  force
      .nodes(nodes)
      .links(links)
      .start();

  var link = svg.selectAll(".link")
      .data(links)
    .enter().append("line");

  var node = svg.selectAll(".node")
      .data(nodes)
    .enter().append("circle")
      .attr("r", 5)
      .call(force.drag);

  force.on("tick", function() {
    link.attr("x1", function(d) { return d.source.x; })
        .attr("y1", function(d) { return d.source.y; })
        .attr("x2", function(d) { return d.target.x; })
        .attr("y2", function(d) { return d.target.y; });

    node.attr("cx", function(d) { return d.x; })
        .attr("cy", function(d) { return d.y; });
  });
});

</script>

graph.json

{
   "1": [ 7,  2,  6],
   "2": [ 8,  3,  1],
   "3": [ 4,  2,  9],
   "4": [10,  3,  5],
   "5": [ 6,  4, 11],
   "6": [ 1,  5, 12],
   "7": [ 1, 20, 13],
   "8": [ 2, 14, 21],
   "9": [ 3, 22, 15],
  "10": [ 4, 16, 23],
  "11": [ 5, 17, 24],
  "12": [ 6, 19, 18],
  "13": [ 7, 19],
  "14": [20,  8],
  "15": [21,  9],
  "16": [22, 10],
  "17": [23, 11],
  "18": [24, 12],
  "19": [12, 13],
  "20": [14,  7],
  "21": [ 8, 15],
  "22": [ 9, 16],
  "23": [10, 17],
  "24": [11, 18]
}