对链接列表进行插入排序时遇到问题。 当我尝试按升序对列表进行排序时，仅打印列表的第一个值

Question

I am writing a program for one of my classes and am stuck on the section that asks to sort a linked list in ascending order. I have tried to sort the list but when I run the function it only prints the first value. I know the print function works because I can run it without Insert Sort and it prints fine.

My code is as follows:

#include "linkedList.h"
#include <stdlib.h>
#include <stdio.h>


void swap(struct Link *first, struct Link *second){
  struct Link* temp = first;
  temp->next = first->next;
  temp->value = first->value;
  first = second;
  first->next = second->next;
  first->value = second->value;
  second = temp;
  second->next = temp->next;
  second->value = temp->value;
}

struct Link* listInsertionSort(struct Link* head) {

  /*
   * This function should perform an insertion sort on the list whose head is
   * provided as the function's argument, so that the values in the list are
   * sorted in ascending order, starting at the head.
   *
   * The sort should be done without allocating any new Link structs or any
   * other auxiliary data structures.
   *
   * Return a pointer to the new head of the list.
   */

struct Link* cur = head;
cur->next = head->next;
struct Link* count;
for(;cur->next != NULL; cur = cur->next){
  for(count = cur->next; count != NULL; count = count->next){
      if(cur->value < count->value){
        swap(cur, count);
      }
  }
}


return cur;

}

And the linkedList.h file is here:

#ifndef __LINKEDLIST_H
#define __LINKEDLIST_H

#define TYPE int

/* Single link structure */
struct Link {
  TYPE value;
  struct Link* next;
};

struct Link* listInsertionSort(struct Link* head);
struct Link* reverseList(struct Link* head);
struct Link* reverseListRecursive(struct Link* head);

#endif

And the test file is here (Although there shouldn't be any error here since this was provided to all students in the class by our instructor):

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <float.h>

#include "linkedList.h"

struct Link* buildLink(int n, int rev, int mod) {
  struct Link* head = (struct Link*)malloc(sizeof(struct Link));
  struct Link* cur = head;

  for (int i = 0; i < n; i++) {
    if (rev)
      cur->value = n - i - 1; //If rev is 1, creates list from high value to low value
    else
      cur->value = i; //If rev is 0, creates list from low value to high value

    if (mod)
      cur->value = cur->value % mod; //Modifies list so that it increments up to value of mod

    if (i + 1 < n)
      cur->next = (struct Link*)malloc(sizeof(struct Link)); //Creates next link in the array
    else
      cur->next  = 0; //If less than the cap it sets next character to NULL, ending the list
    cur = cur->next; //Sets current link to next link to continue for loop
  }

  return head;
}

void printLL(struct Link* l,char* s) {
  printf("LL %s: ",s);
  while (l != 0) {
    printf("%d ", l->value);
    l = l->next;
  }
  printf("\n");
}

int main() {
  // We aren't practicing good memory management
  //    here....
  struct Link* l = buildLink(10, 0, 4);
  struct Link* r = listInsertionSort(l);
  printLL(r, "Sort 0-9 mod 4"); //This should print 0 0 0 1 1 1 2 2 3 3

}

Does anyone have any idea what the problem is here? The error is somewhere in listInsertionSort(struct Link* head) but I have tried multiple different combinations with no success.

The current output is : LL Sort 0-9 mod 4: 1 When it should be: LL Sort 0-9 mod 4: 0 0 0 1 1 1 2 2 3 3

Answer 1

I found the solution for the problem I was having.

Instead of returning cur, I was supposed to return head. I also changed the swap function so that it did not include swapping values of the links in the list because that was unnecessary and looked messy.