我收到的提示要求使用 c 语言的程序来实现链接列表，并为用户提供在链接列表上执行不同功能的选项。需要的功能是:
- isempty():检查列表是否为空并返回指示是否为空的值
- add():向列表尾部添加一个元素
- insert():在列表中的特定索引处插入元素
- find():查找存储特定值的索引。 。如果函数失败，则返回一个值，表明
- get():获取存储在特定索引处的值
- remove():删除列表中第一次出现的特定值。如果函数失败，则返回一个指示该值的值
- replace():替换存储在特定索引处的值
- delete():删除特定索引处的元素。 。如果函数失败，则返回一个值，表明
- list():以[a, b, c]的格式打印列表的元素
当我调用 add_tail 函数时，它允许我输入我想要添加的值，但大约一分钟后，我在终端中收到一条消息，说程序已被终止。可能是什么原因造成的？我还遇到了主函数中用于打印菜单并获取用户输入的 while 循环的问题。当我第一次运行程序时，菜单将正常打印，但在操作完成后，菜单打印一次但跳过用户输入，然后再次打印但接受用户输入第二次。
头文件:
#ifndef LAB8_H_
#define LAB8_H_
#define FIND 'F'
#define EMPTY 'E'
#define ADD 'A'
#define INSERT 'I'
#define DELETE 'D'
#define REMOVE 'R'
#define REPLACE 'S'
#define GET 'G'
#define LIST 'L'
#define QUIT 'Q'
#define FAIL -100
struct node_t {
struct node_t * next;
int value;
};
struct node_t * create_node(int value);
struct node_t * add_tail(struct node_t * head, int value);
struct node_t * insert_node(struct node_t * head, int index, int value);
int is_empty(struct node_t * head);
int find_val(struct node_t * head, int value);
int get_value(struct node_t * head, int index);
struct node_t * replace_val(struct node_t * head, int index, int value);
struct node_t * remove_val(struct node_t * head, int value);
struct node_t * delete_node(struct node_t * head, int index);
void print_list(struct node_t * head);
#endif
.c 文件:
#include <stdio.h>
#include <stdlib.h>
#include "func.h"
struct node_t * create_node(int value)
{
struct node_t * new_node = malloc(sizeof(struct node_t));
new_node -> next = NULL;
new_node -> value = value;
return new_node;
}
struct node_t * add_tail(struct node_t * head, int value)
{
struct node_t * tmp;
if(head == NULL){
printf("Cannot add tail to an empty list. Try again\n");
return NULL;
} else{
while(head != NULL){
if(head -> next == NULL){
tmp = create_node(value);
head -> next = tmp;
} else{
head = head -> next;
}
}
}
return head;
}
struct node_t * insert_node(struct node_t * head, int index, int value)
{
struct node_t * tmp;
struct node_t * new;
if(index < 0){
printf("Index cannot be a negative number. Please try again\n");
return head;
}
if(index == 0){
tmp = head;
head = create_node(value);
head -> next = tmp;
} else {
tmp = head;
while(tmp != NULL){
if (index == 1){
struct node_t * prev = tmp;
tmp = tmp -> next;
new = create_node(value);
new -> next = tmp;
prev -> next = new;
head = prev;
} else if((tmp -> next == NULL) && (index != 0)){
printf("The index is not found in the bounds of the list. Try again\n");
return head;
} else{
tmp = tmp -> next;
index--;
}
}
}
return head;
}
int is_empty(struct node_t * head)
{
if(head == NULL){
return 0;
} else{
return 1;
}
}
int find_val(struct node_t * head, int value)
{
int index = 0;
if(head == NULL){
printf("Cannot find value in empty list! Try again\n");
index = -100;
} else{
while(head != NULL){
if((head -> next == NULL) && (head -> value != value)){
printf("The value does not exist in the list\n");
index = -100;
} else if(head -> value == value){
return index;
} else{
head = head -> next;
index++;
}
}
}
return index;
}
int get_value(struct node_t * head, int index)
{
int value;
if(index < 0){
printf("Index cannot be a negative number. Try again\n");
value = -100;
} else if(head == NULL){
printf("Cannot find index in empty list. Try again\n");
value = -100;
} else{
while(head != NULL){
if(index == 0){
value = head -> value;
} else if((head -> next == NULL) && (index != 0)){
printf("Index does not exist in the bounds of the list. Try again\n");
value= -100;
} else{
head = head -> next;
index--;
}
}
}
return value;
}
struct node_t * replace_val(struct node_t * head, int index, int value)
{
struct node_t * tmp;
if(index < 0){
printf("Index cannot be a negative number. Try again\n");
return NULL;
} else if(head == NULL){
printf("Cannot replace elements in an empty list. Try again\n");
return NULL;
} else{
while(head != NULL){
if (index == 0){
tmp = head;
tmp -> value = value;
free(head);
head = tmp;
} else if((head -> next == NULL) && (index != 0)){
printf("Index does not exist is the bounds of the list. Try again\n");
return NULL;
} else{
head = head -> next;
index--;
}
}
}
return head;
}
struct node_t * remove_val(struct node_t * head, int value)
{
struct node_t * tmp;
if(head == NULL){
printf("Value cannot be found in an empty list. Try again\n");
return NULL;
} else{
while(head != NULL){
if((head -> next == NULL) && (head -> value != value)){
printf("The value does not exist in the list. Try again\n");
return NULL;
} else if(head -> next -> value == value){
tmp = head -> next;
head -> next = tmp -> next;
free(tmp);
} else{
head = head -> next;
}
}
}
return head;
}
struct node_t * delete_node(struct node_t * head, int index)
{
struct node_t * tmp;
if(index < 0){
printf("Index cannot be a negative number. Try again\n");
return NULL;
} else if(head == NULL){
printf("Cannot delete elements from an empty list. Try again\n");
return NULL;
} else{
while(head != NULL){
if((head -> next == NULL) && (index != 0)){
printf("The index is not found in the bounds of the list. Try again\n");
return NULL;
} else if(index == 1){
tmp = head;
head = head -> next;
tmp -> next = head -> next;
head -> next = NULL;
free(head);
head = tmp;
} else{
head = head -> next;
index--;
}
}
}
return head;
}
void print_list(struct node_t * head)
{
if (head == NULL){
printf("The list is empty. Nothing to print\n");
} else{
while(head != NULL){
if(head -> next != NULL){
printf("%d, ", head -> value);
} else{
printf("%d", head -> value);
}
head = head -> next;
}
}
}
主文件:
#include <stdio.h>
#include <stdlib.h>
#include "func.h"
int main(void)
{
struct node_t * head = NULL;
int index, value;
char choice;
int cont = 0;
while(cont == 0){
printf("Welcome to the Linked List operator. Here are the functions that can be performed:\n");
printf("A) Add element to the end of the list\n");
printf("I) Insert and element at a specific index\n");
printf("E) Check if the list is empty\n");
printf("F) Find a value in the list and return the index\n");
printf("G) Get the value at a specific index\n");
printf("S) Replace the value at a specific index\n");
printf("R) Remove the first occurance of a specific value\n");
printf("D) Delete the element at a specific index\n");
printf("L) List all the elements currently stored\n");
printf("Q) Quit the program\n");
printf("Please enter which action you would like to perform: ");
scanf("%c", &choice);
switch(choice){
case ADD:
printf("Please enter the value you would like to add: ");
scanf("%d", &value);
head = add_tail(head, value);
break;
case INSERT:
printf("Please enter the index at which you want to insert a new element: ");
scanf("%d", &index);
printf("Please enter the value you would like to insert: ");
scanf("%d", &value);
head = insert_node(head, index, value);
break;
case EMPTY:
if(is_empty(head) == 0){
printf("The list is empty!\n");
} else if(is_empty(head) == 1){
printf("The list is not empty!\n");
} else{
printf("Something went wrong\n");
}
break;
case FIND:
printf("Please enter the value that you would like to find in the list: ");
scanf("%d", &value);
index = find_val(head, value);
if(index == FAIL){
printf("Error. Try again\n");
} else{
printf("The index that the value %d exists at is %d\n", value, index);
}
break;
case GET:
printf("Please enter the index for which you would like to know the value: ");
scanf("%d", &index);
if(value == FAIL){
printf("Error. Try again\n");
} else{
printf("The value of the element at index %d is %d\n", index, value);
}
break;
case REPLACE:
printf("Please enter the index of the element that you would like to replace: ");
scanf("%d", &index);
printf("Please enter the new value: ");
scanf("%d", &value);
if(replace_val(head, index, value) == NULL){
printf("Error. Could not replace node\n");
} else{
printf("Success. Here is the new list:\n");
print_list(head);
}
break;
case REMOVE:
printf("Please enter the value that you would like to remove the first occurance of: ");
scanf("%d", &value);
if(remove_val(head, value) == NULL){
printf("Error. Could not remove node\n");
} else{
printf("Success! Here is the new list:\n");
print_list(head);
}
break;
case DELETE:
printf("Please enter the index of the element you would like to delete: ");
scanf("%d", &index);
if(delete_node(head, index) == NULL){
printf("Error. Could not delete selected element\n");
} else{
printf("Success! Here is the new list:\n");
print_list(head);
}
break;
case LIST:
printf("[");
print_list(head);
printf("]\n");
break;
case QUIT:
printf("You have chosen to quit the program. Goodbye!\n");
cont = 1;
break;
default:
printf("You entered an invalid choice. Please try again. Goodbye!\n");
}
}
return 0;
}
最佳答案
函数 add_tail 中的 if 语句
if(head == NULL){
printf("Cannot add tail to an empty list. Try again\n");
return NULL;
没有意义。应该将其删除。
在函数的 while 循环内，指针 head 发生变化。
while(head != NULL){
if(head -> next == NULL){
tmp = create_node(value);
head -> next = tmp;
} else{
head = head -> next;
}
}
添加节点后循环不会中断。它将再次添加一个新节点。即无限循环。
但是即使你会插入break语句
while(head != NULL){
if(head -> next == NULL){
tmp = create_node(value);
head -> next = tmp;
break;
} else{
head = head -> next;
}
}
函数返回的指针将不是指向链表头节点的指针。
该函数可以通过以下方式定义
struct node_t * add_tail( struct node_t *head, int value )
{
struct node_t *new_node = create_node( value );
if ( head == NULL )
{
head = new_node;
}
else
{
struct node_t *current = head;
while ( current->next != NULL ) current = current->next;
current->next = new_node;
}
return head;
}
我确信您的程序中的代码还存在其他问题。您可以在更新您在此问题中引用的函数 add_tail 后提出新问题。
关于c - C 中链表的问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/75942953/