C程序遍历单链表

Question

我编写了一个 C 程序来实现遍历单链表的概念。该程序首先通过请求用户输入来创建列表，然后显示/遍历创建的列表。当我运行此代码时，它成功创建链接列表，但在显示创建的列表时，它会产生无限循环。 `

#include<stdio.h>
#include<stdlib.h>
struct node{
    int data;
    struct node *next;
} *head;

int main(){
    struct node *newNode, *temp;
    int n;
    printf("Enter number of Nodes: ");
    scanf("%d",&n);
    if(n <= 1){
        printf("Invalid Input Nodes should Nodes should be greater than 1");
        exit(0);
        
        }
        else{
    head = (struct node *)malloc(sizeof(struct node));
    if(head == NULL){
        printf("No Memory Allocation");
        exit(0);
        }
        else{
            printf("Node Data 1: ");
            scanf("%d",&head -> data);
            head -> next = NULL;
            temp = head;
            }
    newNode = (struct node *)malloc(sizeof(struct node));
    if(newNode == NULL){
        printf("No Memory Allocation");
        exit(0);
        }
        else{
        for(int i = 2; i <= n; ++i){
            printf("Node Data %d: ",i);
            scanf("%d",&newNode -> data);
            newNode -> next = NULL; 
            temp -> next = newNode;  
            temp = temp -> next;
            
            }
        }
        
    //Traversal        
       struct node *ptr;     
        ptr = head;   
        if(ptr == NULL)  
        {  
            printf("Empty list..");  
        }  
        else  
        {   
            while (ptr != NULL){  
                printf("\n%d",ptr->data);  
                ptr = ptr -> next;  
            }  
        }  
    }
    return 0;
}

`

Answer 1

在此 for 循环中，

    for(int i = 2; i <= n; ++i){
        printf("Node Data %d: ",i);
        scanf("%d",&newNode -> data);
        newNode -> next = NULL;
        temp -> next = newNode;
        
        }

同一指针 newNode 被分配给数据成员 temp->next，这相当于表达式 head->next，因为在循环内指针 temp 未更改。

您需要在循环中分配新节点并重新分配指针 temp。

您还需要检查输入的变量n 值。例如，如果n设置为1，那么就会出现内存泄漏。

如果输入的变量 n 值不等于 INT_MAX，则不会出现无限循环。

该程序可以如下所示

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

int main( void )
{
    struct node 
    {
        int data;
        struct node *next;
    } *head = NULL;

    unsigned int n = 0;

    printf( "Enter number of Nodes: " );
    scanf( "%u", &n );

    if (n != 0)
    {
        head = malloc( sizeof( struct node ) );

        if (!head)
        {
            puts( "No Memory Allocation" );
            exit( 0 );
        }
        else 
        {
            printf( "Node Data 1: " );
            scanf( "%d", &head->data );
            head->next = NULL;
        
            unsigned int i = 0;
            for (struct node *temp = head;  ++i < n; temp = temp->next)
            {
                if (( temp->next = malloc( sizeof( struct node ) ) ) == NULL)
                {
                    puts( "No Memory Allocation" );
                    break;
                }
                temp->next->next = NULL;
                printf( "Node Data %u: ", i + 1 );
                scanf( "%d", &temp->next->data );
            }

            for (const struct node *current = head; current != NULL; current = current->next)
            {
                printf( "%d -> ", current->data );
            }

            puts( "null" );
        }
    }
}

程序输出是

Enter number of Nodes: 5
Node Data 1: 1
Node Data 2: 2
Node Data 3: 3
Node Data 4: 4
Node Data 5: 5
1 -> 2 -> 3 -> 4 -> 5 -> null

请注意，您需要在程序中附加将释放所有已分配内存的代码。