povtornyy-ekzamen-graf-s-refleksiey-i-do/SOLUTION.md

What was implemented

• Added a ReflectionNode class that can duplicate the outgoing edges of a target node (reflect method).
• Added a RewritingNode class that can replace a target node with a new one (rewrite method).
• Extended Graph with replaceNode to preserve edges during a rewrite and traverse for DFS traversal.

Why the main parts satisfy the requirements

• The assignment explicitly asks for “узлы рефлексии и переписывания”.
• ReflectionNode.reflect creates a new node (${targetId}_ref) and copies all edges from the original target, ensuring the reflected node behaves like the original.
• RewritingNode.rewrite calls Graph.replaceNode, which removes the old node, rewires all incoming edges to the new node, and keeps the outgoing edges intact.
• Tests confirm that reflected nodes exist, have the correct type, and preserve edges; that rewriting removes the old node and connects the new one; and that traversal still visits all nodes without duplication.

Short code excerpts

src/index.js – ReflectionNode

class ReflectionNode extends Node {
  reflect(graph) {
    const targets = graph.edges.get(this.id) || new Set();
    for (const targetId of targets) {
      const targetNode = graph.getNode(targetId);
      if (!targetNode) continue;
      const newId = `${targetId}_ref`;
      if (graph.getNode(newId)) continue;
      const newNode = new Node(newId, targetNode.type);
      graph.addNode(newNode);
      const targetTargets = graph.edges.get(targetId) || new Set();
      for (const tt of targetTargets) {
        graph.addEdge(newId, tt);
      }
    }
  }
}

src/index.js – RewritingNode

class RewritingNode extends Node {
  rewrite(graph, targetId, newNode) {
    graph.replaceNode(targetId, newNode);
  }
}

src/index.js – Graph.replaceNode

replaceNode(oldId, newNode) {
  const oldTargets = this.edges.get(oldId) ? new Set(this.edges.get(oldId)) : new Set();
  this.edges.delete(oldId);
  this.nodes.delete(oldId);
  this.addNode(newNode);
  for (const [from, targets] of this.edges.entries()) {
    if (targets.has(oldId)) {
      targets.delete(oldId);
      targets.add(newNode.id);
    }
  }
  for (const target of oldTargets) {
    this.addEdge(newNode.id, target);
  }
}

Honest limitations

• Reflection only copies outgoing edges; incoming edges to the original node are not duplicated.
• replaceNode rewires edges but does not detect or handle cycles that could arise during a rewrite.
• The DFS traversal is simple and may not be optimal for very large graphs, but it suffices for the assignment’s test cases.

These additions bring the solution in line with the assignment’s requirement to include reflection and rewriting nodes.