如何從一個Singly linked linear list中刪除資料

要從一個singly lisked linerar list中刪除文件，最簡單的方式莫過於用一個指標指向前一個node，如果現在的item需要刪除，將前面一項item指向後面的item即可。

typedef struct node  
{
    struct node * next; 
} node;  

node *remove_if(node * head, remove_fn rm)
{       
    for (node *prev = NULL, *curr = head; curr != NULL; )   
    {   
            node * next = curr->next;  
            if (rm(curr))  
            {   
                    if (prev)  
                            prev->next = curr->next;  
                    else  
                            head = curr->next;  
                    free(curr);  
            }   
            else  
                    prev = curr;  
            curr = next;  
    }   
    return head;  
}

有人提出了更精巧的方法，利用two star pointer來達成，也就是指標的指標。

void remove_if(node **head, remove_fn rm)
{
    for (node** curr = head; *curr; )
    {
            node * entry = *curr;
            if (rm(entry))
            {
                    *curr = entry->next;
                    free(entry);
            }
            else
                    curr = &entry->next;
    }
}

在C++11的年代，增加了forward_list，省得自己造輪子的麻煩。
以下是forward_list的介紹。

std::forward_list is a container that supports fast insertion and removal of elements from anywhere in the container. Fast random access is not supported. It is implemented as singly-linked list and essentially does not have any overhead compared to its implementation in C. Compared to std::list this container provides more space efficient storage when bidirectional iteration is not needed.

以下是一個示範程式，裡面同時使用了lambda expression跟Range-based for loop，日後有時間在寫。

#include <iostream>
#include <forward_list>
int main()
{
    std::forward_list<int> list = {8, 7, 5, 3, 2, 6, 4};
    list.remove_if([](int n) { return n % 2 == 0; }); 

    for (int n : list) {
        std::cout << n << ' '; 
    }   
    std::cout << '\n';
}