krahets/hello-algo · error · RangeError

Index Out Of Bounds Exception

Error message

Index Out Of Bounds Exception

What it means

Thrown by GraphAdjMat.removeVertex() (a RangeError) when index >= this.size() (i.e. >= vertices.length). Note the guard is asymmetric: it checks the upper bound only and does NOT reject negative index, so a negative index will slip through to Array.splice and be interpreted as an offset-from-end — a latent bug rather than a thrown error for negatives. The intent is to block deletion of a non-existent vertex position.

Source

Thrown at codes/typescript/chapter_graph/graph_adjacency_matrix.ts:52

        const n: number = this.size();
        // 向顶点列表中添加新顶点的值
        this.vertices.push(val);
        // 在邻接矩阵中添加一行
        const newRow: number[] = [];
        for (let j: number = 0; j < n; j++) {
            newRow.push(0);
        }
        this.adjMat.push(newRow);
        // 在邻接矩阵中添加一列
        for (const row of this.adjMat) {
            row.push(0);
        }
    }

    /* 删除顶点 */
    removeVertex(index: number): void {
        if (index >= this.size()) {
            throw new RangeError('Index Out Of Bounds Exception');
        }
        // 在顶点列表中移除索引 index 的顶点
        this.vertices.splice(index, 1);

        // 在邻接矩阵中删除索引 index 的行
        this.adjMat.splice(index, 1);
        // 在邻接矩阵中删除索引 index 的列
        for (const row of this.adjMat) {
            row.splice(index, 1);
        }
    }

    /* 添加边 */
    // 参数 i, j 对应 vertices 元素索引
    addEdge(i: number, j: number): void {
        // 索引越界与相等处理
        if (i < 0 || j < 0 || i >= this.size() || j >= this.size() || i === j) {
            throw new RangeError('Index Out Of Bounds Exception');

View on GitHub (pinned to 69932aed18)

Solutions

1. Validate both bounds yourself: if (index >= 0 && index < graph.size()) graph.removeVertex(index).
2. Treat the vertex index as a positional cursor that shifts after every removeVertex — recompute or iterate carefully when removing multiple vertices (remove highest index first).
3. If you mean to remove by value, find its index via graph.vertices.indexOf(val) and confirm >= 0.
4. Fix the class guard to also reject index < 0 if you control the source.

Example fix

// before
graph.removeVertex(index); // throws if index >= size
// after
if (index >= 0 && index < graph.size()) graph.removeVertex(index);
// when removing several, go high-to-low to keep indices stable
indices.sort((a, b) => b - a).forEach(i => { if (i < graph.size()) graph.removeVertex(i); });

function safeRemoveVertex(graph, index) {
  // guard BOTH bounds: the class only checks the upper bound
  if (index >= 0 && index < graph.size()) { graph.removeVertex(index); return true; }
  return false;
}

null

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When it happens

Trigger: Calling removeVertex(index) with index >= number of vertices; calling on a graph that was shrunk below a stale index captured earlier. A negative index does not throw here but instead splices from the end — still a logic error, just silent.

Common situations: Using a stale vertex count after prior removeVertex calls shrank the array; off-by-one loop using <= size; confusing vertex value with vertex index (the matrix is indexed by position, not by the stored value).

Related errors

• Index Out Of Bounds Exception
• Illegal Argument Exception
• Index out of bounds
• Illegal Argument Exception
• Illegal Argument Exception

AI-assisted analysis of krahets/hello-algo@69932aed18 (2026-08-13). Data as JSON: /api/errors/72f26281c2b10bcd. Report an issue: GitHub.