krahets/hello-algo · error

邊索引越界或相等

Error message

邊索引越界或相等

What it means

Traditional-Chinese localization of the addEdge guard (see error 602). addEdge forbids negative/out-of-range endpoints and self-loops (i == j) because this is a simple undirected graph. Logged to stderr; adjMat unchanged.

Source

Thrown at zh-hant/codes/c/chapter_graph/graph_adjacency_matrix.c:80

    for (int i = index; i < graph->size - 1; i++) {
        for (int j = 0; j < graph->size; j++) {
            graph->adjMat[i][j] = graph->adjMat[i + 1][j];
        }
    }
    // 在鄰接矩陣中刪除索引 index 的列
    for (int i = 0; i < graph->size; i++) {
        for (int j = index; j < graph->size - 1; j++) {
            graph->adjMat[i][j] = graph->adjMat[i][j + 1];
        }
    }
    graph->size--;
}

/* 新增邊 */
// 參數 i, j 對應 vertices 元素索引
void addEdge(GraphAdjMat *graph, int i, int j) {
    if (i < 0 || j < 0 || i >= graph->size || j >= graph->size || i == j) {
        fprintf(stderr, "邊索引越界或相等\n");
        return;
    }
    graph->adjMat[i][j] = 1;
    graph->adjMat[j][i] = 1;
}

/* 刪除邊 */
// 參數 i, j 對應 vertices 元素索引
void removeEdge(GraphAdjMat *graph, int i, int j) {
    if (i < 0 || j < 0 || i >= graph->size || j >= graph->size || i == j) {
        fprintf(stderr, "邊索引越界或相等\n");
        return;
    }
    graph->adjMat[i][j] = 0;
    graph->adjMat[j][i] = 0;
}

/* 列印鄰接矩陣 */

View on GitHub (pinned to 69932aed18)

Solutions

1. Pass indices, not values.
2. Insert both vertices first.
3. Forbid i == j at the call site.

Example fix

// before
addEdge(graph, 1, 3);

// after
int i = indexOf(graph, 1), j = indexOf(graph, 3);
if (i >= 0 && j >= 0 && i != j) addEdge(graph, i, j);

static inline int graphValidEdge(const GraphAdjMat *g, int i, int j) {
    return g != NULL && i >= 0 && j >= 0
        && i < g->size && j < g->size && i != j;
}

if (graphValidEdge(graph, i, j)) addEdge(graph, i, j);

When it happens

Trigger: addEdge(graph, i, j) with i/j out of range or equal — typically vertex values mistaken for indices, or a self-loop.

Common situations: Value-vs-index confusion; self-loops; edges created before endpoints are inserted.

Related errors

• Edge index out of bounds or equal
• 辺インデックスが範囲外であるか、同一です
• индексы ребра выходят за границы или совпадают
• 頂點索引越界
• 边索引越界或相等

AI-assisted analysis of krahets/hello-algo@69932aed18 (2026-08-13). Data as JSON: /api/errors/c30b230d9751d348. Report an issue: GitHub.