上海xx 双向链表 面试题 list node

#include<iostream>  
#include<cstdio>  
#include<string>  
#include<malloc.h>  
using namespace std;  
  
typedef struct mylist  
{  
    void* head;  
    void* tail;  
} List,*pList;  
  
typedef struct mynode  
{  
    void* next;  
    void* prev;  
    int data;  
} Node,*pNode;  
  
pList createlist()  
{  
    pList root;  
    pNode temp;  
    int n;  
    root = (pList)malloc(sizeof(List));  
    root->head = NULL;  
    root->tail = NULL;  
    printf("input data number:");  
    scanf("%d",&n);  
    if(n&&NULL==root->head)  
    {  
        temp = (pNode)malloc(sizeof(Node));  
        printf("data1:");  
        scanf("%d",&temp->data);  
        temp->next = (pList)root;  
        temp->prev = (pList)root;  
        root->head = (pNode)temp;  
        root->tail = (pNode)temp;  
        n--;  
    }  
    for(int i=1; i<=n ; i++)  
    {  
        temp = (pNode)malloc(sizeof(Node));  
        printf("data%2d:",i);  
        scanf("%d",&temp->data);  
        temp->next = (pList)root;  
        temp->prev = (pNode)root->tail;  
        ((pNode)(root->tail))->next = (pNode)temp;  
        root->tail = (pNode)temp;  
    }  
    return root;  
}  
  
void printlist(pList root)  
{  
    pNode temp = (pNode)root->head;  
    int i = 1;  
    while(temp!=(pNode)root)  
    {  
        printf("data%2d:%d\n",i++,temp->data);  
        temp = (pNode)temp->next;  
    }  
  
    /*temp = (pNode)root->tail; 
    while(temp!=(pNode)root) 
    { 
        printf("data%2d:%d\n",--i,temp->data); 
        temp = (pNode)temp->prev; 
    }*/  
}  
  
int main()  
{  
    pList root;  
    root = createlist();  
    printlist(root);  
}  

双向链表的面试题要求list和node是不同的结构体，所以这里使用的void指针
1声明LIst和Node结构体
2创建链表
3尾部追加
4头部删除
都很简单，我只写了创建 打印时测试用的，主要就是试试void类型的指针用法
上面的所有都加上了显示类型转换
以下去掉了不必要的类型转换
总结一下，
1.当给void类型指针赋值的时候不需要显示类型转换
2.void给void赋值不需要转换
3.当void给其他类型的指针赋值时需要显示类型转换
4.当void*与不同类型的指针比较的时候需要显示类型转换
5.当需要链式的时候需要显示类型转换。
注释标记对应1，2，3，4，5的情况
注意：不转换不等于不需要转换，而是编译器隐式转换了

#include<iostream>  
#include<cstdio>  
#include<string>  
#include<malloc.h>  
using namespace std;  
  
typedef struct mylist  
{  
    void* head;  
    void* tail;  
} List,*pList;  
  
typedef struct mynode  
{  
    void* next;  
    void* prev;  
    int data;  
} Node,*pNode;  
  
pList createlist()  
{  
    pList root;  
    pNode temp;  
    int n;  
    root = (pList)malloc(sizeof(List));         //malloc属于情况3  
    root->head = NULL;  
    root->tail = NULL;  
    printf("input data number:");  
    scanf("%d",&n);  
    if(n&&NULL==root->head)  
    {  
        temp = (pNode)malloc(sizeof(Node));   //3  
        printf("data1:");  
        scanf("%d",&temp->data);  
        temp->next = root;            //1  
        temp->prev = root;            //1  
        root->head = temp;           //1  
        root->tail = temp;              //1  
        n--;  
    }  
    for(int i=1; i<=n ; i++)  
    {  
        temp = (pNode)malloc(sizeof(Node));  //3  
        printf("data%2d:",i);  
        scanf("%d",&temp->data);  
        temp->next = root;                   //1  
        temp->prev = root->tail;          //2  
        ((pNode)(root->tail))->next = temp; //5  
        root->tail = temp;  //1  
    }  
    return root;  
}  
  
void printlist(pList root)  
{  
    pNode temp = (pNode)root->head;   //3  
    int i = 1;  
    while(temp!=(pNode)root)                  //4  
    {  
        printf("data%2d:%d\n",i++,temp->data);  
        temp = (pNode)temp->next;          //3  
    }  
  
    /*temp = (pNode)root->tail; 
    while(temp!=(pNode)root) 
    { 
        printf("data%2d:%d\n",--i,temp->data); 
        temp = (pNode)temp->prev; 
    }*/  
}  
  
int main()  
{  
    pList root;  
    root = createlist();  
    printlist(root);  
}