我正在研究练习题的测试，似乎无法使我的链表能够正常地使用递归删除链表中元素的函数。以下是我的完整代码，如果您发现我可以改进其他方法，请告诉我。谢谢！ ：）
/*
Q1:
Try implementing the functions shown in class on your own:
check: node creation
check: insertion at the end of a linked list,
check: insertion at the head of a linked list,
check: a list printing function.
Q2:
check: Write a recursive printList() function.
Q3:
check: Write a recursive tailInsert() function.
Q4:
check: Write a function that inserts nodes at the beginning of the linked list.
Q5:
check: Write a recursive function that prints a linked list in reverse order.
The function signature is: void printReverse(node *head);
Q6:
- Write an iterative destroyList() function that frees all the nodes in a linked list.
Q7:
- Now implement destroyList() recursively.
Q8:
- Write a function that deletes the nth element from a linked list.
If the linked list doesn't even have n nodes, don't delete any of them.
The function signature is: node *deleteNth(node *head, int n).
- Try implementing the function iteratively and recursively.
- (In terms of how to interpret n, you can start counting your nodes from zero or one; your choice.)
Q9:
- Write a function that deletes every other element in a linked list.
- (Try writing it both ways: one where it starts deleting at the head of the list,
- and one where it starts deleting at the element just after the head of the list.)
- Can you write this both iteratively and recursively?
Q10:
- Write a function that deletes all even integers from a linked list.
Q11:
- Write a function that takes a sorted linked list and an element to be inserted into that linked list,
and inserts the element in sorted order.
The function signature is: node *insertSorted(node *head, int n);
Q12:
- One of the problems with the first insertNode() function from today is that it
requires us to call it using head = insertNode(head, i).
That's a bit dangerous, because we could forget the "head =" part very easily.
Re-write the function so that it takes a pointer to head,
thereby allowing it to directly modify the contents of head without any need for a return value.
The function signature is: void insertNode(node **head, int data).
The function will be called using insertNode(&head, i).
*/
//come back to
#include <stdio.h>
#include <stdlib.h>
// Basic linked list node struct; contains 'data' and 'next' pointer.
// What happens if we type "node *next" instead of "struct node *next"?
typedef struct node
{
// data field
int data;
// the next node in the list
struct node *next;
} node;
// Allocate a new node. Initialize its fields. Return the pointer.
// We call this from our insertion functions.
node *createNode(int data)
{
node *ptr = NULL;
ptr = malloc(sizeof(node));
if(ptr == NULL)
{
printf("space could not be allocated\n");
return NULL;
}
ptr->data = data;
ptr->next = NULL;
return ptr;
}
// Insert into the end of the linked list. Return the head of the linked list.
// (What is the order (Big-Oh) of this function?)
node *insertNode(node *head, int data)
{
node *temp;
if (head == NULL)
return createNode(data);
for(temp = head; temp->next != NULL; temp = temp->next)
;
temp->next = createNode(data);
return head;
}
node *insertNodeFront(node *head, int data)
{
node *temp;
if(head == NULL)
return createNode(data);
temp = createNode(data);
temp->next = head;
return temp;
}
// Simple function to print the contents of a linked list.
void printList(node *head)
{
if (head == NULL)
{
printf("Empty List\n");
return;
}
for(; head != NULL; head = head->next)
printf("%d ", head->data);
printf("\n");
}
void printListRecursiveHelper(node *head)
{
if (head == NULL)
return;
printf("%d%c", head->data, (head->next == NULL) ? '\n' : ' ');
printListRecursiveHelper(head->next);
}
void printListRecursive(node *head)
{
if (head == NULL)
{
printf("empty list\n");
return;
}
printListRecursiveHelper(head);
}
// Q3: - Write a recursive tailInsert() function.
node *tailInsert(node *head, int data)
{
if(head->next == NULL)
{
node *temp;
temp = createNode(data);
temp->next = NULL;
head->next = temp;
return temp;
}
return tailInsert(head->next, data);
}
//Q5: Write a recursive function that prints a linked list in reverse order.
void printReverse(node *head)
{
if (head == NULL)
return;
printReverse(head->next);
printf("%d ", head->data);
}
// Q6: - Write an iterative destroyList() function that frees all the nodes in a linked list.
// Got code from internet, memorize it
/* Function to delete the entire linked list */
void destroyList (struct node** head)
{
struct node* current = *head;
struct node* next;
while (current != NULL)
{
next = current->next;
free(current);
current = next;
}
*head = NULL;
}
//Q7: - Now implement destroyList() recursively.
// Look up online, need to examine why it deson't work
node *destroyListRecursive(node *head)
{
if ( head == NULL)
return NULL;
destroyListRecursive(head->next);
free(head);
}
int main(void)
{
int i, r;
// The head of our linked list. If we don't initialize it to NULL, our
// insertNode() function might segfault.
node *head = NULL;
srand(time(NULL));
// Populate the linked list with random integers. We are inserting into the
// head of the list each time.
for (i = 0; i < 10; i++)
{
printf("Inserting %d...\n", r = rand() % 20 + 1);
head = insertNode(head, r);
}
head = insertNodeFront(head, 1);
tailInsert(head, 5);
// Print the linked list.
printList(head);
printf("\n");
printReverse(head);
printf("\n\n");
// Print the linked list using our recursive function.
printListRecursive(head);
//destroyList(&head);
head = destroyListRecursive(head);
printList(head);
system("PAUSE");
return 0;
}
答案 0 :(得分：1)
这是基于我[和其他人]的热门评论，但是这很有用[很抱歉只发布main中的一行更改以及函数的重写整个程序：
/*
Q1:
Try implementing the functions shown in class on your own:
check: node creation
check: insertion at the end of a linked list,
check: insertion at the head of a linked list,
check: a list printing function.
Q2:
check: Write a recursive printList() function.
Q3:
check: Write a recursive tailInsert() function.
Q4:
check: Write a function that inserts nodes at the beginning of the linked list.
Q5:
check: Write a recursive function that prints a linked list in reverse order.
The function signature is: void printReverse(node *head);
Q6:
- Write an iterative destroyList() function that frees all the nodes in a linked list.
Q7:
- Now implement destroyList() recursively.
Q8:
- Write a function that deletes the nth element from a linked list.
If the linked list doesn't even have n nodes, don't delete any of them.
The function signature is: node *deleteNth(node *head, int n).
- Try implementing the function iteratively and recursively.
- (In terms of how to interpret n, you can start counting your nodes from zero or one; your choice.)
Q9:
- Write a function that deletes every other element in a linked list.
- (Try writing it both ways: one where it starts deleting at the head of the list,
- and one where it starts deleting at the element just after the head of the list.)
- Can you write this both iteratively and recursively?
Q10:
- Write a function that deletes all even integers from a linked list.
Q11:
- Write a function that takes a sorted linked list and an element to be inserted into that linked list,
and inserts the element in sorted order.
The function signature is: node *insertSorted(node *head, int n);
Q12:
- One of the problems with the first insertNode() function from today is that it
requires us to call it using head = insertNode(head, i).
That's a bit dangerous, because we could forget the "head =" part very easily.
Re-write the function so that it takes a pointer to head,
thereby allowing it to directly modify the contents of head without any need for a return value.
The function signature is: void insertNode(node **head, int data).
The function will be called using insertNode(&head, i).
*/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
// Basic linked list node struct; contains 'data' and 'next' pointer.
// What happens if we type "node *next" instead of "struct node *next"?
typedef struct node {
// data field
int data;
// the next node in the list
struct node *next;
} node;
// Allocate a new node. Initialize its fields. Return the pointer.
// We call this from our insertion functions.
node *
createNode(int data)
{
node *ptr = NULL;
ptr = malloc(sizeof(node));
if (ptr == NULL) {
printf("space could not be allocated\n");
return NULL;
}
ptr->data = data;
ptr->next = NULL;
return ptr;
}
// Insert into the end of the linked list. Return the head of the linked list.
// (What is the order (Big-Oh) of this function?)
node *
insertNode(node * head, int data)
{
node *temp;
if (head == NULL)
return createNode(data);
for (temp = head; temp->next != NULL; temp = temp->next);
temp->next = createNode(data);
return head;
}
node *
insertNodeFront(node * head, int data)
{
node *temp;
if (head == NULL)
return createNode(data);
temp = createNode(data);
temp->next = head;
return temp;
}
// Simple function to print the contents of a linked list.
void
printList(node * head)
{
if (head == NULL) {
printf("Empty List\n");
return;
}
for (; head != NULL; head = head->next)
printf("%d ", head->data);
printf("\n");
}
void
printListRecursiveHelper(node * head)
{
if (head == NULL)
return;
printf("%d%c", head->data, (head->next == NULL) ? '\n' : ' ');
printListRecursiveHelper(head->next);
}
void
printListRecursive(node * head)
{
if (head == NULL) {
printf("empty list\n");
return;
}
printListRecursiveHelper(head);
}
// Q3: - Write a recursive tailInsert() function.
node *
tailInsert(node * head, int data)
{
if (head->next == NULL) {
node *temp;
temp = createNode(data);
temp->next = NULL;
head->next = temp;
return temp;
}
return tailInsert(head->next, data);
}
// Q5: Write a recursive function that prints a linked list in reverse order.
void
printReverse(node * head)
{
if (head == NULL)
return;
printReverse(head->next);
printf("%d ", head->data);
}
// Q6: - Write an iterative destroyList() function that frees all the nodes in a linked list.
// Got code from internet, memorize it
/* Function to delete the entire linked list */
void
destroyList(struct node **head)
{
struct node *current = *head;
struct node *next;
while (current != NULL) {
next = current->next;
free(current);
current = next;
}
*head = NULL;
}
// Q7: - Now implement destroyList() recursively.
// Look up online, need to examine why it deson't work
node *
destroyListRecursive(node * head)
{
if (head != NULL) {
destroyListRecursive(head->next);
free(head);
}
return NULL;
}
int
main(void)
{
int i,
r;
// The head of our linked list. If we don't initialize it to NULL, our
// insertNode() function might segfault.
node *head = NULL;
srand(time(NULL));
// Populate the linked list with random integers. We are inserting into the
// head of the list each time.
for (i = 0; i < 10; i++) {
printf("Inserting %d...\n", r = rand() % 20 + 1);
head = insertNode(head, r);
}
head = insertNodeFront(head, 1);
tailInsert(head, 5);
// Print the linked list.
printList(head);
printf("\n");
printReverse(head);
printf("\n\n");
// Print the linked list using our recursive function.
printListRecursive(head);
// destroyList(&head);
head = destroyListRecursive(head);
printList(head);
system("PAUSE");
return 0;
}