c - 当我删除第一个节点时，它会生成无限循环错误

Question

当我删除第一个节点时，我的代码给出无限循环错误，其他删除没问题。

#include <stdio.h>
#include <stdlib.h>
 struct node //Node
 {
  int info;
  struct node * link;
 };
//insertion at begin
struct node * AddAtBegin(struct node * start, int data) {
 struct node * p;
 p = (struct node * ) malloc(sizeof(struct node));
 p - > info = data;
 p - > link = start;
 start = p;
 return start;
}

//insertion at End
struct node * AddAtEnd(struct node * start, int data) {
  struct node * p, * q = start;
  p = (struct node * ) malloc(sizeof(struct node));
  p - > info = data;
  p - > link = NULL;
  while (q - > link != NULL)
   q = q - > link;
  q - > link = p;
  return start;
 }
 //insertion after any given node
struct node * AddAfter(struct node * start, int data, int node) {
 if (node == ' ')
  return start;
 struct node * temp, * p = start;
 temp = (struct node * ) malloc(sizeof(struct node));
 temp - > info = data;
 while (p != NULL) {
  if (p - > info == node) {
   temp - > link = p - > link;
   p - > link = temp;
   return start;
  }
  p = p - > link;
 }
 printf("Not Found Your Node");
 return start;
}

//insertion before any given node
struct node * AddBefore(struct node * start, int data, int node) {
  if (start == NULL) {
   printf("List is Empty");
   return start;
  }
  struct node * p, * q = start;
  p = (struct node * ) malloc(sizeof(struct node));
  p - > info = data;

  if (start - > info == node) {
   p - > link = start;
   start = p;
   return start;
  }
  while (q - > link != NULL) {
   if (q - > link - > info == node) {
    p - > link = q - > link;
    q - > link = p;
    return start;
   }
   q = q - > link;
  }
  printf("NOT found node");
  return start;
 }
 // deletion of node
int Delete(struct node * start, int data) {
  struct node * p = start;
  struct node * temp = NULL;

  if (start == NULL) {
   printf("Epty list");
   exit(1);
  }
  if (p - > info == data) {
   temp = start;
   start = p - > link;
   free(temp);
   printf("After Deletion of %d == ", data);
   return 0;
  }
  while (p - > link != NULL) {
   if (p - > link - > info == data) {
    temp = p - > link;
    p - > link = temp - > link;
    free(temp);
    printf("After Deletion of %d == ", data);
    return 0;
   }
   p = p - > link;
  }
  printf("Not Found In The List");
  return 0;
 }
 //display of all nodes 
void Display(struct node * start) {
 struct node * p = start;
 while (p != NULL) {
  printf("%d \t", p - > info);
  p = p - > link;
 }
 return;
}
int main() {
 struct node * start = NULL;
 int i;
 start = AddAtBegin(start, 2);
 start = AddAtBegin(start, 1);
 start = AddAtEnd(start, 4);
 start = AddAtEnd(start, 5);
 start = AddAfter(start, 6, 5);
 start = AddAfter(start, 3, 2);
 start = AddBefore(start, 7, 6);
 start = AddBefore(start, 79, 1);
 printf("List is \n");
 Display(start);
 printf("\n");
 scanf("%d", & i);
 Delete(start, i);
 Display(start);
 Delete(start, 7);
 Display(start);
 Delete(start, 79);
 Display(start);
 return 0;
}

Answer 1

这是因为 start 在 C 中是按值传递的。对 start 的更改不会反射(reflect)在调用者中。相反，传递一个指向 start 的指针。

// deletion of node
int Delete(struct node ** start, int data) {
  struct node *p = start;
  struct node *temp = NULL;
  if (p - > info == data) {
   temp = start;
   *start = p - > link;
   return 0;
  }
  // other cases
}