// https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/breadth-first-search

function bfs(graph, root) {
  const nodesLen = {};
  const n_nodes = graph[root].length;
  for (let dst = 0; dst < n_nodes; dst++) {
    nodesLen[dst] = Infinity;
  }
  nodesLen[root] = 0;
  for (let q = [root], d = 1; ; d++) {
    const newQ = [];
    for (let src of q) {
      for (let dst = 0; dst < n_nodes; dst++) {
        if (nodesLen[dst] > d && graph[src][dst] > 0) {
          nodesLen[dst] = d;
          newQ.push(dst);
        }
      }
    }
    if (newQ.length <= 0) {
      break;
    }
    q = newQ;
  }
  return nodesLen;
}

var exBFSGraph = [
  [0, 1, 0, 0],
  [1, 0, 1, 0],
  [0, 1, 0, 1],
  [0, 0, 1, 0],
];
console.log(bfs(exBFSGraph, 3));