嘗試運行鏈表C程序時出錯

Question

我是編程新手，所以這里的問題是，當我想執行以下程序時，但這僅表明該程序已停止工作。我不知道代碼有什么問題，因為沒有編譯錯誤。任何幫助將不勝感激。

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

struct ppl
{
    char name[30];
    struct ppl *next;
};

main()
{

    struct ppl *student1, *student2, *student3, *student4, *temp, *ptr, *x;
    struct ppl *head = NULL;
    int no;

    head = (struct ppl *)malloc(sizeof(struct ppl));
    student1 = (struct ppl *)malloc(sizeof(struct ppl));
    student2 = (struct ppl *)malloc(sizeof(struct ppl));
    student3 = (struct ppl *)malloc(sizeof(struct ppl));
    student4 = (struct ppl *)malloc(sizeof(struct ppl));

    head->next = student1;
    strcpy(student1->name, "Aizar");

    student1->next = student2;
    strcpy(student2->name, "Chandi");

    student2->next = student3;
    strcpy(student3->name, "Faizul");

    student3->next = student4;
    strcpy(student4->name, "Joshua");
    student4->next = NULL;

    ptr = head;
    while (ptr->next != NULL)
    {
        ptr = (struct ppl *)malloc(sizeof(struct ppl));
        ptr = ptr->next;
        printf("Name list : %s \n", ptr);

    };

    return 0;
}

Answer 1

問題出在while循環內。 嘗試這個：

while(ptr->next != NULL)
{
 ptr = ptr->next; 
    printf("Name list : %s \n", ptr );

};

PS： ptr不需要單獨的內存分配。 它將指向由分配給它的指針所指向的內存位置（在while循環中）。

Answer 2

注意 ： don't give me fish teach me how to fish

一些評論：

 ptr = head; // here ptr has the value of head
    while (ptr->next != NULL)
    {
        ptr = (struct ppl *)malloc(sizeof(struct ppl)); // ptr loses the value of head and takes new value given by malloc
        ptr = ptr->next; // ptr -> next is null so ptr becomes null
        printf("Name list : %s \n", ptr); // generally if you want to print pointers use %p not %s 

    };

一些跡象：

1. 我認為您要打印學生姓名而不是指針。
2. 不需要為ptr分配內存，因為在while循環之前，它需要head的值。

現在輪到您根據需要更正代碼了。

快樂編碼：D

Answer 3

我認為您的意思是：。）

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

struct ppl
{
    char name[30];
    struct ppl *next;
};

int main( void )
{

    struct ppl *student1, *student2, *student3, *student4, *temp;
    struct ppl *head = NULL;

    student1 = (struct ppl *)malloc( sizeof( struct ppl ) );
    student2 = (struct ppl *)malloc( sizeof( struct ppl ) );
    student3 = (struct ppl *)malloc( sizeof( struct ppl ) );
    student4 = (struct ppl *)malloc( sizeof( struct ppl ) );

    strcpy( student1->name, "Aizar" );
    student1->next = student2;

    strcpy( student2->name, "Chandi" );
    student2->next = student3;

    strcpy( student3->name, "Faizul" );
    student3->next = student4;

    strcpy( student4->name, "Joshua" );
    student4->next = NULL;

    head = student1;

    for ( temp = head; temp != NULL; temp = temp->next )
    {
        printf( "Student Name: %s \n", temp->name );
    }

    while ( head )
    {
        temp = head;
        head = head->next;
        free( temp );
    }

    return 0;
}

程序輸出為

Student Name: Aizar 
Student Name: Chandi 
Student Name: Faizul 
Student Name: Joshua 

至於你的代碼，那么這個循環

while (ptr->next != NULL)
{
    ptr = (struct ppl *)malloc(sizeof(struct ppl));
    ptr = ptr->next;
    printf("Name list : %s \n", ptr);

};

沒有道理。

另外，您無需為磁頭分配單獨的節點。 頭應該是指向第一個分配的“學生”的指針。

考慮到C函數主要應具有返回類型int