jane-street: answer facts problem (https://www.youtube.com/watch?v=V8DGdPkBBxg)

facts.js

const facts = [
  ['m', 3.28, 'ft'],
  ['m', 100, 'cm'],
  ['ft', 12, 'in'],
  ['hr', 60, 'min'],
  ['min', 60, 'sec'],
];

const construct_graph = (facts) => {
  const graph = {};
  for (let i = 0; i < facts.length; ++i) {
    const n = facts[i][0];
    const m = facts[i][2];
    const val = facts[i][1];

    if (graph[n]) {
      graph[n].push([m, val]);
    } else {
      graph[n] = [[m, val]];
    }
    if (graph[m]) {
      graph[m].push([n, 1 / val]);
    } else {
      graph[m] = [[n, 1 / val]];
    }
  }
  return graph;
};

function dfs(graph, start, end, visited, path) {
  visited[start] = true;
  for (let i = 0; i < graph[start].length; ++i) {
    const curr_node = graph[start][i][0];
    const unit_val = graph[start][i][1];
    if (!visited[curr_node]) {
      path.push([curr_node, unit_val]);
      dfs(graph, curr_node, end, visited, path, start);
    }
  }
}

const calc_query = (val, from, to) => {
  const graph = construct_graph(facts);
  const p = [[from, 1]];
  dfs(graph, from, to, {}, p);
  let res = val;
  console.log(p);
  let invalid = true;
  for (let i = 0; i < p.length; i++) {
    const [name, val] = p[i];
    res *= val;
    if (name == to) {
      invalid = false;
      break;
    }
  }
  return invalid ? 'invalid conversion' : res;
};

const rs = calc_query(30, 'min', 'hr');
console.log(rs);