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fix: handle dangling pointer #1381

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fix: handle dangling pointer #1381

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35 changes: 25 additions & 10 deletions codes/c/chapter_graph/graph_adjacency_list.c
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Original file line number Diff line number Diff line change
Expand Up @@ -38,11 +38,13 @@ GraphAdjList *newGraphAdjList() {
void delGraphAdjList(GraphAdjList *graph) {
for (int i = 0; i < graph->size; i++) {
AdjListNode *cur = graph->heads[i];
if (cur == NULL) {
continue;
}
cur = cur->next;
while (cur != NULL) {
AdjListNode *next = cur->next;
if (cur != graph->heads[i]) {
free(cur);
}
free(cur);
cur = next;
}
free(graph->heads[i]->vertex);
Expand All @@ -61,6 +63,14 @@ AdjListNode *findNode(GraphAdjList *graph, Vertex *vet) {
return NULL;
}

AdjListNode** findNodeV2(GraphAdjList *graph, Vertex *vet) {
for (int i = 0; i < graph->size; i++) {
if (graph->heads[i]->vertex == vet) {
return &(graph->heads[i]);
}
}
}

/* 添加边辅助函数 */
void addEdgeHelper(AdjListNode *head, Vertex *vet) {
AdjListNode *node = (AdjListNode *)malloc(sizeof(AdjListNode));
Expand Down Expand Up @@ -119,15 +129,17 @@ void addVertex(GraphAdjList *graph, Vertex *vet) {

/* 删除顶点 */
void removeVertex(GraphAdjList *graph, Vertex *vet) {
AdjListNode *node = findNode(graph, vet);
AdjListNode **node = findNodeV2(graph, vet);
assert(node != NULL);
// 在邻接表中删除顶点 vet 对应的链表
AdjListNode *cur = node, *pre = NULL;
while (cur) {
pre = cur;
cur = cur->next;
free(pre);
AdjListNode **cur_ref = node, **pre_ref = NULL;
while (*cur_ref) {
pre_ref = cur_ref;
*cur_ref = ((*cur_ref)->next);
free(*pre_ref);
*pre_ref = NULL;
}
AdjListNode *cur = NULL, *pre = NULL;
// 遍历其他顶点的链表，删除所有包含 vet 的边
for (int i = 0; i < graph->size; i++) {
cur = graph->heads[i];
Expand All @@ -145,7 +157,7 @@ void removeVertex(GraphAdjList *graph, Vertex *vet) {
// 将该顶点之后的顶点向前移动，以填补空缺
int i;
for (i = 0; i < graph->size; i++) {
if (graph->heads[i] == node)
if (graph->heads[i] == *node)
break;
}
for (int j = i; j < graph->size - 1; j++) {
Expand All @@ -160,6 +172,9 @@ void printGraph(const GraphAdjList *graph) {
printf("邻接表 =\n");
for (int i = 0; i < graph->size; ++i) {
AdjListNode *node = graph->heads[i];
if (node == NULL) {
continue;
}
printf("%d: [", node->vertex->val);
node = node->next;
while (node) {
Expand Down