Dart solution to https://www.reddit.com/r/dailyprogrammer/comments/4ijtrt/20160509_challenge_266_easy_basic_graph/

dp-266-node-degrees.dart

import "dart:io";
import "dart:convert";

int main() async {
  Map<int, List<int>> nodes = {};
  int maxNodes = null;
  List<int> emptyNode() => new List<int>.filled(maxNodes, 0);

  // initialises node if it doesn't yet exist
  List<int> node(int i) {
    if(nodes[i] == null) nodes[i] = emptyNode();
    return nodes[i];
  }

  List<int> intArray(String line) {
    return line.split(" ").map(int.parse).toList();
  }

  // I store edges in a 2D array just so it's easier for me to
  // print the matrix at the end
  addEdge(int from, int to) {
    node(from)[to - 1] = 1;
    node(to)[from - 1] = 1;
  }

  processEdge(List<int> edge) {
    if(maxNodes == null) maxNodes = edge[0];
    else addEdge(edge[0], edge[1]);
  }

  // stdin streams bytes, so they need to be converted
  // Not sure if I could convert them to integers directly
  Stream nodeStream = stdin
    .transform(UTF8.decoder)
    .transform(const LineSplitter())
    .map(intArray);

  await nodeStream.listen(processEdge).asFuture();

  StringBuffer matrix = new StringBuffer("\n\nMatrix: \n");
  RegExp tokens = new RegExp(r'[\[\],]');
  for (int i = 1; i <= maxNodes; i++) {
    print("Node $i has a degree of ${node(i).where((edge) => edge == 1).length}");
    matrix.writeln("  " + node(i).toString().replaceAll(tokens, ''));
  }

  print(matrix);
  return 0;
}