Question

我试图通常添加到链接列表，因为我有2个链接列表，我为这两个列表调用相同的函数。

void addToList(void* (*createNode)(void *data,char* name), int (compare)(void *a1, void *a2), void *(*getNext)(void), void(*setNext)(void *node, void* data), void *data,char* name, void **list) {
void *node = createNode(data,name);

void *head = *list;
if (head == NULL) { // if list is empty
    *list = node;
}
else if (compare(head, node)) { // if first element is greater than node to add (meaning we need to add node to head of list)
    setNext(node, list);
    *list = node;
}
else {
    // node will be inserted someplace other than head
    void *current = head;
    while (getNext(current) != NULL && compare(node, getNext(current))) {
        // loop until we are at the end of the list OR until we have found an element greater than us
        // basically, current will be the place to put the new node in
        current = getNext(current);
    }
    setNext(node, getNext(current));
    setNext(current, node);
}

这是结构，列表和节点

struct Stud {//my struct contains 2 lists
int id;
float gradeAverage;
float incomeAverage;
struct gradeList *gradelist;
struct incomeList *incomelist;
};

typedef struct Stud Students;

struct gradeNode {//the grade node with what is inside it
 char courseName[20];
 int grade;
 struct gradeNode *next;
 struct gradeNode *prev;
  };
  struct gradeList {//my first list with head and tail
  struct gradeNode *head;
  struct gradeNode *tail;
  int size;
   };

   struct incomeNode {//my secound node 
   char *workplace;
   float income;
   struct incomeNode *next;
      struct incomeNode *prev;
     };
      struct incomeList {//the secount list
     struct incomeNode *head;
     struct incomeNode *tail;
     int size;
    };

以下是我使用的功能

       void* get_next_Income(void* head) {//used above in the generic call
       return((struct incomeNode *)head)->next;
                         }
         void* get_next_Grade(void* head) {//used above to get the income

     return(((struct gradeNode *)head)->next);
      }


            int compareGradeNode(void *a1, void *a2) {//compares the node iam adding to the exicting node and adding accordingly
     return ((struct gradeNode*)a1)->grade > ((struct gradeNode*)a2)->grade;
               }
      int compareIncomeNode(void *a1, void *a2) {
      return ((struct incomeNode*)a1)->income>((struct incomeNode*)a2)-
      >income;
 }
    void setNextGradeNode(void* node, void* data) {//seting the next graded
    ((struct gradeNode*)node)->next = data;
                         }
          void setNextIncomeNode(void* node, void* data) {//setting the next income
    ((struct incomeNode*)node)->next = data;
             }
            Students students[30];
              int numOfStuds = 0;

             void* createGradeNode(void* data,char*name) {  
 struct gradeNode* nd=(struct GradeNode*)malloc(sizeof(struct gradeNode));
 strcpy(nd->courseName, name);
  assert(nd != NULL);
 nd->grade = data;//setting the new  node to the data the user entered!
 nd->next = NULL;
 return nd;//and return it
  }

问题是我在下面的代码部分得到了一个空ptr 我正在使用visual studio而无法解决它请帮忙。很抱歉长代码，我是c的新手。

void *head = *list;
if (head == NULL) { // if list is empty
    *list = node;

添加到链表通常为nullptr问题

0 个答案: