问题描述

c语言单向链表的问题？？？

 #include<stdio.h>#include<stdlib.h>struct node{    int num;    struct node *next;};//构建空的链表struct node* InitList(struct node *L){    L = (struct node*)malloc(sizeof(struct node));    L = NULL;    printf_s(""InitList sucess!"");    return L;}//创建单链表struct node* CreateList(struct node *Lint n){    struct node *temp*p;    L = (struct node*)malloc(sizeof(struct node));    L->next = NULL;    temp=L;    for (int i = 0; i < n; i++){        p = (struct node*)malloc(sizeof(struct node));        scanf_s(""%d"" &p->num);        temp->next = p;        temp = p;    }    temp->next = NULL;    return L;}void PrintList(struct node *L){    struct node *temp = L;    while (temp != NULL){        printf_s(""%d"" temp->num);        temp = temp->next;    }}void PrintMenu(){    printf_s(""------Menu------
"");    printf_s(""0  InitList
"");    printf_s(""1  CreateList
"");    printf_s(""2  PrintList
"");}void main(){    int nc;    struct node *La;    PrintMenu();    printf_s(""Enter the command: "");    scanf_s(""%d"" &c);    switch (c){    case 0:        La = InitList(La);        break;    case 1:        printf_s(""Enter the number of LinkList: "");        scanf_s(""%d"" &n);        La = CreateList(La n);        break;    case 2:        PrintList(La);        break;    default:        printf_s(""ERROREnter again: "");        break;    }    system(""pause"");}

为什么主函数case 0 的La = InitList(La); 这句报错： error C4700: uninitialized local variable 'La' used。 ？？？？

解决方案

完善了一下，头结点没存数，print时要从第二个开始：

 #include<stdio.h>#include<stdlib.h>struct node{    int num;    struct node *next;};//构建空的链表void InitList(struct node *&L){//修改    L = (struct node*)malloc(sizeof(struct node));    L->next = NULL;    L->num=0;    printf_s(""InitList sucess!"");}//创建单链表void CreateList(struct node *&Lint n){//修改    struct node *temp*p;    L = (struct node*)malloc(sizeof(struct node));    L->next = NULL;    L->num=0;    temp=L;    for (int i = 0; i < n; i++){        p = (struct node*)malloc(sizeof(struct node));        scanf_s(""%d"" &p->num);        temp->next = p;        temp = p;    }    temp->next = NULL;}void PrintList(struct node *L){    struct node *temp = L->next;//修改，头结点不使用    while (temp != NULL){        printf(""%d"" temp->num);        temp = temp->next;    }}void PrintMenu(){    printf_s(""------Menu------
"");    printf_s(""0  InitList
"");    printf_s(""1  CreateList
"");    printf_s(""2  PrintList
"");}void main(){    int nc;    struct node *La;    c=1;    while(c>=0)    {        PrintMenu();        printf_s(""Enter the command: "");        scanf_s(""%d"" &c);        switch (c){        case 0:            InitList(La);            break;        case 1:            printf_s(""Enter the number of LinkList: "");            scanf_s(""%d"" &n);            CreateList(La n);            break;        case 2:            PrintList(La);            break;        default:            printf_s(""ERROREnter again: "");            break;        }    }    struct node *te;//增加释放空间    if(La)    {        te=La->next;        free(La);        La=te;    }    system(""pause"");}

解决方案二：
struct node *La;
->
struct node *La = (node *)malloc(sizeof(node));

解决方案三：
C语言之单向链表
C语言实现链表之单向链表（十五）测试用例
C语言单向循环链表解决约瑟夫问题

解决方案四：
可以用引用。给你改了一部分，自己再完善吧，还需要free

 #include<stdio.h>#include<stdlib.h>struct node{    int num;    struct node *next;};//构建空的链表void InitList(struct node *&L){//修改    L = (struct node*)malloc(sizeof(struct node));    L = NULL;    printf_s(""InitList sucess!"");}//创建单链表void CreateList(struct node *&Lint n){//修改    struct node *temp*p;    L = (struct node*)malloc(sizeof(struct node));    L->next = NULL;    temp=L;    for (int i = 0; i < n; i++){        p = (struct node*)malloc(sizeof(struct node));        scanf_s(""%d"" &p->num);        temp->next = p;        temp = p;    }    temp->next = NULL;}void PrintList(struct node *L){    struct node *temp = L;    while (temp != NULL){        printf_s(""%d"" temp->num);        temp = temp->next;    }}void PrintMenu(){    printf_s(""------Menu------
"");    printf_s(""0  InitList
"");    printf_s(""1  CreateList
"");    printf_s(""2  PrintList
"");}void main(){    int nc;    struct node *La;    c=1;    while(c>=0)    {        PrintMenu();        printf_s(""Enter the command: "");        scanf_s(""%d"" &c);        switch (c){        case 0:            InitList(La);//修改            break;        case 1:            printf_s(""Enter the number of LinkList: "");            scanf_s(""%d"" &n);            CreateList(La n);//修改            break;        case 2:            PrintList(La);            break;        default:            printf_s(""ERROREnter again: "");            break;        }    }    system(""pause"");}