在c程序中用struct定义链表结构

Question

我用一个C程序创建了一个链表。我的代码如下:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
struct node {
int data;
int key;
struct node *next;
};
struct node *current = NULL;
struct node *head = NULL;
int numberOfElements = 0;
//display the list
void printList() {
struct node *ptr = head;
printf("n[ ");

//start from the beginning
while(ptr != NULL) {
printf("(%d,%d) ",ptr->key,ptr->data);
ptr = ptr->next;
}

printf(" ]");
}
//insert link at the first location
void insertFirst(int key, int data) {
//create a link
struct node *link = (struct node*) malloc(sizeof(struct node));

link->key = key;
link->data = data;

//point it to old first node
link->next = head;

//point first to new first node
head = link;
numberOfElements ++;
}
//delete first item
struct node* deleteFirst() {
//save reference to first link
struct node *tempLink = head;


//mark next to first link as first 
head = head->next;

//return the deleted link

return tempLink;
numberOfElements --;
}
//is list empty
bool isEmpty() {
return head == NULL;
}
int length() {

return numberOfElements;
}
//find a link with given key
struct node* find(int key) {
//start from the first link
struct node* current = head;
//if list is empty
if(head == NULL) {
return NULL;
}
//navigate through list
while(current->key != key) {

//if it is last node
if(current->next == NULL) {
return NULL;
} else {
//go to next link
current = current->next;
}
}      

//if data found, return the current Link
return current;
}
//delete a link with given key
struct node* delete(int key) {
numberOfElements --;
//start from the first link
struct node* current = head;
struct node* previous = NULL;

//if list is empty
if(head == NULL) {
return NULL;
}
//navigate through list
while(current->key != key) {
//if it is last node
if(current->next == NULL) {
return NULL;
} else {
//store reference to current link
previous = current;
//move to next link
current = current->next;
}
}
//found a match, update the link
if(current == head) {
//change first to point to next link
head = head->next;
} else {
//bypass the current link
previous->next = current->next;
}    

return current;
}

void main() {
insertFirst(1,10);
insertFirst(2,20);
insertFirst(3,30);
insertFirst(4,1);
insertFirst(5,40);
insertFirst(6,56); 
printf("Original List: "); 

//print list
printList();
printf("nlength is %dn",length());

struct node *foundLink = find(4);

if(foundLink != NULL) {
printf("nElement found: ");
printf("(%d,%d) ",foundLink->key,foundLink->data);
printf("n");  
} else {
printf("Element not found.");
}
delete(4);
printf("List after deleting an item: ");
printList();
printf("n");
foundLink = find(4);

if(foundLink != NULL) {
printf("nElement found: ");
printf("(%d,%d) ",foundLink->key,foundLink->data);
printf("n");
} else {
printf("Element not found.");
}
printf("nlength is %dn",length());

}

在链表结构中，我只将节点结构定义为结构体，没有将链表结构定义为单独的结构体。通过为链表结构定义一个单独的结构体，如下所示;

struct MyList {
struct node *head;
int numberOfElements;
};

我想从全局可变性中排除变量'head'和'numberOfElements'。有了这个更改，我如何更新上面的代码并运行它?

Answer 1

最简单的解决方案是修改您的列表管理函数，使它们采用struct MyList*参数，并将对head和numberOfElements的所有引用更改为list->head和list->numberOfElements，然后将struct MyList放在任何函数中使用它(在您的情况下为main())，并将对struct MyList的引用传递给需要修改它的每个函数，例如:

//find a link with given key
struct node* find(struct MyList *list,int key) {
//start from the first link
struct node* current = list->head;
//if list is empty
if(list->head == NULL) {
return NULL;
...

//is list empty
bool isEmpty(struct MyList *list) {
return list->head == NULL;
}
int length(struct MyList *list) {

return list->numberOfElements;
}

int main(){
struct MyList list = (struct MyList){.head=NULL, .numberOfElements = 0};
insertFirst(&list,1,10);
insertFirst(&list,2,20);
insertFirst(&list,3,30);
insertFirst(&list,4,1);
...