krahets/hello-algo · warning
图的顶点数量已达最大值
Error message
图的顶点数量已达最大值
What it means
Printed to stderr by addVertex in the GraphAdjMat teaching class (an adjacency-matrix undirected graph) when graph->size == MAX_SIZE (100). Unlike the Ruby implementations which raise exceptions, this C function merely prints the message and returns silently — it does NOT set errno, return an error code, or abort. The vertex is silently not added, so the caller has no programmatic way to detect the failure except by checking preconditions beforehand.
Source
Thrown at codes/c/chapter_graph/graph_adjacency_matrix.c:39
GraphAdjMat *graph = (GraphAdjMat *)malloc(sizeof(GraphAdjMat));
graph->size = 0;
for (int i = 0; i < MAX_SIZE; i++) {
for (int j = 0; j < MAX_SIZE; j++) {
graph->adjMat[i][j] = 0;
}
}
return graph;
}
/* 析构函数 */
void delGraphAdjMat(GraphAdjMat *graph) {
free(graph);
}
/* 添加顶点 */
void addVertex(GraphAdjMat *graph, int val) {
if (graph->size == MAX_SIZE) {
fprintf(stderr, "图的顶点数量已达最大值\n");
return;
}
// 添加第 n 个顶点，并将第 n 行和列置零
int n = graph->size;
graph->vertices[n] = val;
for (int i = 0; i <= n; i++) {
graph->adjMat[n][i] = graph->adjMat[i][n] = 0;
}
graph->size++;
}
/* 删除顶点 */
void removeVertex(GraphAdjMat *graph, int index) {
if (index < 0 || index >= graph->size) {
fprintf(stderr, "顶点索引越界\n");
return;
}
// 在顶点列表中移除索引 index 的顶点View on GitHub (pinned to 69932aed18)
Solutions
- Check graph->size < MAX_SIZE before calling addVertex.
- Increase the MAX_SIZE #define at the top of the file (or in common.h) and recompile if your dataset requires more vertices.
- Call removeVertex to free a slot before adding a new vertex when at capacity.
- Redirect stderr to a log file and scan for this message during testing.
Example fix
// before
addVertex(graph, val); // silently fails if size == 100
// after
if (graph->size < MAX_SIZE) {
addVertex(graph, val);
} else {
// handle capacity exhaustion: resize MAX_SIZE or remove a vertex
} Defensive patterns
Strategy: validation
Validate before calling
if (graph->size < MAX_SIZE) {
addVertex(graph, val);
} Type guard
/* C: precondition check before addVertex */
static inline bool can_add_vertex(const GraphAdjMat *g) {
return g->size < MAX_SIZE;
} Prevention
- C has no exceptions — the only defense is checking graph->size < MAX_SIZE before the call.
- The function returns void and does NOT set errno, so you cannot detect failure after the call.
- Increase MAX_SIZE at compile time if your dataset needs more than 100 vertices.
- Remove unused vertices with removeVertex to free slots before adding new ones.
When it happens
Trigger: Calling addVertex when the graph already contains exactly MAX_SIZE (100) vertices. This happens after 100 successful addVertex calls without any removeVertex calls, or if MAX_SIZE was lowered.
Common situations: Loading a graph dataset with more than 100 nodes; forgetting that MAX_SIZE is a compile-time #define (100); not calling removeVertex to free slots; increasing graph density without increasing MAX_SIZE.
Related errors
- 顶点索引越界
- 边索引越界或相等
- Graph vertex count has reached maximum
- グラフの頂点数が最大値に達しました
- Количество вершин графа уже достигло максимума
AI-assisted analysis of krahets/hello-algo@69932aed18 (2026-08-13).
Data as JSON: /api/errors/e26a70c45dab27a4.
Report an issue: GitHub.