從 C 中的單鏈表中刪除特定節點

Question

我在 C 中創建了一個單鏈表，我正在嘗試編寫一個 function，它根據 Z157DB7DF530023575515D366C9B672E8 值從列表中刪除特定元素，該值對應於一個特定的節點。

void deleteNodeVar(int val)
{
    struct node *t, *temp, *temp2;

    t = START;
    while(t -> info != val)
    {
        if(t -> ptr == NULL) { break; }
        t = t -> ptr;
    }
    printf("\nfound the val to be %d\n",t -> info);
    temp = t -> ptr;
    t -> ptr = temp -> ptr;
    printf("now will free the node with value %d \n",t -> info);
    free(t);

}

經過一番調試，我發現： function 工作正常，因為它檢測到並成功刪除了節點

但是打印整個列表會產生奇怪的結果。

完整代碼：

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

struct node
{
    int info;
    struct node *ptr;
};

struct node *START = NULL;

struct node* createNode()
{
    struct node *p;
    p = (struct node*) malloc(sizeof(struct node));
    return p;
}

//inserting node
void insertNode(int val)
{
    struct node *temp, *t;
    temp = createNode();
    temp -> info = val;
    temp -> ptr = NULL;

    if(START == NULL){ START = temp; }
    else
    {
        t = START;
        while(t -> ptr != NULL)
        {
            t = t -> ptr;
        }
        t -> ptr = temp;
    }   
}


void pop()
{
    struct node *t;
    t = START;
    if(START == NULL) { printf("THE LIST IS EMPTY\n"); }
    else
    {
        START = START -> ptr;
        free(t);
    }
}

//here are the 2 functions below in which I have problem
void deleteNodeVar(int val)
{
    struct node *t, *temp, *temp2;

    t = START;
    while(t -> info != val)
    {
        if(t -> ptr == NULL) { break; }
        t = t -> ptr;
    }
    printf("\nfound the val to be %d\n",t -> info);
    temp = t -> ptr;
    t -> ptr = temp -> ptr;
    printf("now will free the val with value %d \n",t -> info);
    free(t);

}

void viewList()
{
    struct node *t, *temp;
    t = START;

    while(t != NULL)
    {
        printf("%d -> ",t->info);
        t = t -> ptr;
    }

}

int main() 
{

    insertNode(10);
    insertNode(20);
    insertNode(40);
    insertNode(100);

    viewList();
    int v;
    printf("\nEnter to delete: ");
    scanf("%d",&v);
    deleteNodeVar(v);
    viewList();

}

這是 output 的屏幕截圖，我在刪除值為 40 的節點后嘗試打印列表后得到：

它正在與這些重復值陷入無限循環！

Answer 1

對於初學者來說，當函數依賴於全局變量時，使用全局變量作為指向列表 heda 節點的指針是一個壞主意。 在這種情況下，您無法創建多個列表。

盡管如此，function deleteNodeVar可以通過以下方式定義

int deleteNodeVar(int val)
{
    node *prev = NULL, *current = START;

    while ( current != NULL && current->info != val )
    {
        prev = current;
        current = current->ptr;
    }

    int success = current != NULL;

    if ( success )
    {
        if ( prev == NULL )
        {
            START = START->ptr;
        }
        else
        {
            prev->ptr = current->ptr;
        }

        free( current );
    }

    return success;
}

Answer 2

根據您的刪除 function 如果您要刪除的列表中不存在該節點但即使在您刪除 function 之后也會給出一條消息

found the val to be

這是完全錯誤的......所以你可以這樣寫你的刪除 function

void deleteNodeVar(int val)
{
    node *p ='\0', *n = START;
     int flag=0;

    while ( n != '\0' && n->info != val )
    {
        p =n;
        n =n->ptr;
    }
     if(n!='\0')
          flag=1;


    if ( flag )
    {
        if ( p == '\0' )
        {
            START = START->ptr;
        }
        else
        {
            p->ptr = n->ptr;
        }
              printf("\nfound the val to be %d\n",n-> info);
        free( n );
    }

    else
        printf("The node is not present list\n");
}