[数据结构]双链表

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typedef struct NODE{
    struct NODE *fwd;
    struct NODE *bwd;
    int value;
}Node;

双链表的根节点的bwd指针指向双链表的最后一个节点，fwd指针指向双链表的第一个节点，双链表的value字段为空

以下程序是将一个值插入到一个有序的双链表中，如果链表中已经有和该值相同的节点则不插入

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

typedef struct NODE{
    struct NODE *bwd;
    struct NODE *fwd;
    int value;
}Node;

bool insert(Node *Rootnode,int newvalue);

bool insert(Node *Rootnode,int newvalue)
{
    Node temnode;
    int i = 0;
    temnode = Rootnode;
    Node *newnode = (Node*)malloc(sizeof(Node));
    if(newnode ==NULL)
    {
        printf("malloc fail");
        return false;
    }
    newnode->value = newvalue;
    if (Rootnode->bwd == NULL)
    {
        Rootnode->bwd = newnode;
        Rootnode->fwd = newnode;
        return true;
    }
    for(;temnode->fwd != NULL;temnode = temnode->fwd)
    {
        i++;
        if (temnode->value == newvalue)
        {
            printf("newvalue is already in double link list");
            return true;
        }
        if (temnode->value > newvalue)
        {
            if (i==1)
            {
                newnode->fwd = Rootnode->fwd;
                Rootnode->fwd = newnode;
                newnode->bwd = Rootnode;
                newnode->fwd->bwd=newnode;
            }
            else
            {
                temnode = temnode->bwd;
                newnode->fwd = temnode->fwd;
                temnode->fwd = newnode;
                newnode->bwd = temnode;
                newnode->fwd->bwd=newnode;
            }
        }
        else
        {
            temnode = temnode->bwd;
            newnode = temnode->fwd;
            newnode->bwd = temnode;
        }
    }

    return true;

}