trekhleb/javascript-algorithms · error · Error

Eulerian path must contain two odd-ranked vertices

Error message

Eulerian path must contain two odd-ranked vertices

What it means

Error "Eulerian path must contain two odd-ranked vertices" thrown in trekhleb/javascript-algorithms.

Source

Thrown at src/algorithms/graph/eulerian-path/eulerianPath.js:41

  const isCircuit = !Object.values(oddRankVertices).length;

  if (!isCircuit && Object.values(oddRankVertices).length !== 2) {
    throw new Error('Eulerian path must contain two odd-ranked vertices');
  }

View on GitHub (pinned to 85293e3e2b)

Solutions

1. Add or remove edges so the graph has 0 odd-degree vertices (Eulerian circuit) or exactly 2 (Eulerian path).
2. Check vertex degrees before calling eulerianPath and reject graphs that are not Eulerian.
3. Use a general traversal such as DFS or BFS if the graph is not Eulerian.

When it happens

Trigger: eulerianPath is called on a graph that is not an Eulerian circuit and does not have exactly two odd-degree vertices (e.g. 1, 3, or 4 odd-ranked vertices), so no Eulerian path exists.

Common situations: Running Fleury's algorithm on a graph with 1, 3, or more odd-degree vertices; an Eulerian path requires exactly two odd-degree endpoints.

AI-assisted analysis of trekhleb/javascript-algorithms@85293e3e2b (2026-08-24). Data as JSON: /api/errors/826b15b7c2c84ef5. Report an issue: GitHub.