solve_graph.js

/*
  Description:
  Implement a function solve_graph(start, end, arcs) that will return true if the end node can be reached from the start node,
  using 0 or more arcs. It will return false if it is not possible.
  The graph is defined by a list of arcs, where each arc is an object that has two properties, start and end, representing the
  start and end nodes, respectively. Each arc is unidirectional, in other words it goes from a start node to an end node, and
  not the other way around. Note that 0 or more arcs can leave a node, and 0 or more can arrive to it.
  Note that the solve_graph() method doesn't take a list of nodes as input: for simplicity's sake, let's assume that all nodes
  present in arcs are valid. However, the start or end node may not be in arcs.
  An example
    var arcs = [
      { start : "a", end : "b" },
      { start : "a", end : "a"}
    ];

    solve_graph("a", "b", arcs); // true
    solve_graph("a", "c", arcs); // false
*/

function solve_graph(start, end, arcs) {
  let found = false;
  let neighbors = [];
  arcs.forEach((node) => {if(node.end === end) neighbors.push(node)});
  if (start === end) return arcs.some((n) => n.start === start ? true : false);
  if (neighbors.length === 0) return false;  
  neighbors.forEach((node) => found = node.start === start ? true : solve_graph(start, node.start, arcs));
  return found;
}