插入C中的双向链表

Question

我的程序不断崩溃。我觉得我的逻辑有问题。请帮忙！谢谢

struct node{
    int data;
    struct node *prev,*next;
} *head = NULL;


void insert(){
    struct node* temp = (struct node*) malloc (sizeof (struct node*));
    int value;
    printf("Enter an element");
    scanf("%d",&value);
    temp -> data = value;
    temp -> next = NULL;
    temp -> prev = NULL;
    if(value < head -> data || head == NULL){
        temp -> next = head -> next;
        head = temp;
        return;
    }
    while(head->next != NULL && value > head -> next -> data)
        head = head -> next;
    temp -> next = head ->next->prev;
    head -> next = temp -> prev;
    while (head -> prev != NULL)
        head = head -> prev;
}

Answer 1

首先，想想这两行，如果head==NULL会发生什么：

if(value < head->data || head == NULL){
    temp->next = head->next;

特别是什么是head-

Answer 2

你的空间不够。

改变

struct node* temp = (struct node*) malloc (sizeof (struct node*));

到

struct node* temp = (struct node*) malloc (sizeof (struct node));

Answer 3

试试这个：

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

struct node{
    int data;
    struct node *prev,*next;
} *head = 0;


void insert(int value){
    struct node* temp = (struct node*) malloc (sizeof (struct node));
    //int value;
    //printf("Enter an element");
    //scanf("%d",&value);
    temp -> data = value;
    temp -> next = 0;
    temp -> prev = 0;
    if(head == 0) {
        // no head, make temp the head
        head = temp;
    } else if(value > head->data) {
        // put temp in front of the head
        temp->next = head;
        head->prev = temp;
        head = temp;
    } else {
        // put temp after the head
        struct node *this = head;
        struct node *prev = 0;
        while(this && this->data > value) {
            prev = this;
            this = this->next;
        }
        temp->next = this;
        temp->prev = prev;
        prev->next = temp;
        if(this) {
            this->prev = temp;
        }
    }
}

int main() {
    insert(1);
    insert(3);
    insert(4);
    struct node *t = 0;
    for(t = head; t; t = t->next) {
        printf("%d\n", t->data);
    }
}

这个编译并按降序值排序。注意，我注释了scanf，并使插入取一个参数。