Shortest Path
in Undirected Graph with Unit Distance

function shortestPathUnitWeight(n, edges) {
  const graph = Array.from({ length: n }, () => []);

  // Build the undirected graph
  for (const [u, v] of edges) {
    graph[u].push(v);
    graph[v].push(u);
  }

  const distance = new Array(n).fill(-1);
  const queue = [0];
  distance[0] = 0;

  while (queue.length > 0) {
    const current = queue.shift();
    for (const neighbor of graph[current]) {
      if (distance[neighbor] === -1) {
        distance[neighbor] = distance[current] + 1;
        queue.push(neighbor);
      }
    }
  }

  return distance;
}

// Example usage:
console.log("Shortest distances:", shortestPathUnitWeight(4, [[0,1],[0,2],[1,3]])); // Output: [0,1,1,2]
console.log("Disconnected graph:", shortestPathUnitWeight(3, [[0,1]])); // Output: [0,1,-1]