const compare = (a, b) => a[0] - b[0];
const amount_to_node = amount => [amount];

/* Single commodity, maximum flow, minimum cost optimizer, msand@seaber.io */
function optimize(supplies, demands, costs) {
  const supply_nodes = supplies.map(amount_to_node);
  const demand_nodes = demands.map(amount_to_node);

  const num_supplies = supplies.length;
  const num_demands = demands.length;
  const edges = [];

  for (let from = 0; from < num_supplies; from++) {
    const f = costs[from];
    const supply = supply_nodes[from];
    for (let to = 0; to < num_demands; to++) {
      const demand = demand_nodes[to];
      const cost = f[to];
      edges.push([
        cost,
        supply,
        demand,
        from,
        to,
      ]);
    }
  }

  edges.sort(compare); // Most expensive part of the function

  const num_edges = edges.length; // = num_supplies * num_demands;
  for (let e = 0; e < num_edges; e++) {
    const edge = edges[e];
    const supply = edge[1];
    const demand = edge[2];
    const amount = Math.min(supply[0], demand[0]);
    supply[0] -= amount;
    demand[0] -= amount;
    edge[5] = amount;
  }

  return edges;
}

const supplies = [12, 23];
const demands = [7, 17];
const costs = [[3, 6], [5, 7]];
console.log(optimize(supplies, demands, costs));
```