求助：指针与结构，

做的  指针  链表，del_line,add_line de 指针都是起零时储存作用。
如果输入的是其他的就没问题：如：1 From where does my help come? (Line 2)
就是输：1 Unto the hills I will left up my eyes (Line 1)要出问题，郁闷啊

[[it] 本帖最后由 wolfs 于 2008-3-18 13:30 编辑 [/it]]
----------------解决方案--------------------------------------------------------
head 你有地址吗?
我随便改了下,不改的话编译都不能通过..
#include <iostream>
#include <string>
#include <cstdlib>
using namespace std;
    struct line
    {
    char str[40];
    struct line *next;
    };
int get_choice (struct line *p);
struct line *add_line(struct line *p);
struct line *del_line(struct line *p);

int main ()
    {
    struct line *head;
    int x;
    head=(struct line *)malloc(sizeof(struct line));
    strcpy(head->str,"diyichi");
    head->next=NULL;
    x=get_choice(head);
    for (;x!=3;)
    {
     if (x==1)
     head=add_line(head);
     else
        head=del_line(head);
      x=get_choice(head);
    }
    }
struct line * del_line(struct line *p)
    {
    struct line *p_start,*p_last;
    int i,number;
    cout <<"\tWhich line number?";
    cin >>number;
    if (number==1)
    p_start=p->next;
    else
    {
       for (p_start=p,i=1;i<number;++i,p=p->next)
       p_last=p;
      p_last->next=p->next;
    }
    free(p);
        return (p_start);
    }
    int get_choice(struct line *p)
    {
    int i,choice;
    cout <<"\n...This is the start of your file so far...\n";
    for (i=1;p!=NULL;++i,p=p->next)
         cout <<i<<" "<<p->str<<endl;
    cout <<"...This is the end";
    cout <<"(Enter 1 to Insert,2 to Delete,and 3 to Quit)\n\t";
    cin >>choice;
    return choice;
}
struct line *add_line (struct line *p)
{
    int number,i;
    struct line *p_last, *p_new, *p_start;
    char str_new[40];
    p_start=p;
    p_new=(struct line *)malloc(sizeof(struct line));
    cout <<"First enter the line number and then its contens:\n";
    cin >>number;
    cin.getline(str_new,40);
    for (i=1;i<number;++i,p=p->next)
     p_last=p;
    p_new->next=p;
    strcpy(p_new->str,str_new);
    if (i==1)
    return (p_new);
    else
    {
     p_last->next=p_new;
      return (p_start);
    }
}

[[it] 本帖最后由 sunkaidong 于 2008-3-18 13:43 编辑 [/it]]
----------------解决方案--------------------------------------------------------
head  的地址是malloc分配的啊
运行时输入：1 Unto the hills I will left up my eyes (Line 1)  程序就自动转入 del_line 了，然后就显示说程序错误，需要关闭；  程序原来是要在get_choice中输入  choice=2才会转入 del_line 的
输入其他的就没问题，想不通，是这句话有问题还是程序或编译器的问题

[[it] 本帖最后由 wolfs 于 2008-3-18 15:11 编辑 [/it]]
----------------解决方案--------------------------------------------------------
我帮你改好了..指针是好东西..呵呵
#include <iostream>
#include <string>
#include <cstdlib>
using namespace std;
    struct line
    {
    char str[40];
    struct line *next;
    };
int get_choice (struct line *p);
void add_line(struct line *p);
void  del_line(struct line *p);
int get_choice ();
static int len=0;
struct line *head;
int main ()
    {
    int x;
    head=(struct line *)malloc(sizeof(struct line));
    head->next=NULL;
    x=get_choice();
    for (;x!=3;)
    {
     if (x==1)
     add_line(head);
     else
      del_line(head);
      x=get_choice(head);
    }
    return 1;
    }
void  del_line(struct line *p)
    {
    struct line *p_start,*p_last;
    int i,number;
    cout <<"\tWhich line number?";
    cin >>number;
    if (number==1)
    p_start=p->next;
    else
    {
       for (p_start=p,i=1;i<number;++i,p=p->next)
       p_last=p;
      p_last->next=p->next;
    }
         free(p);
         len--;
        head=p_start;
    }
int get_choice()
    {
    int choice;
    cout <<"\n...This is the start of your file so far...\n";
    cout <<"(Enter 1 to Insert,2 to Delete,and 3 to Quit)\n\t";
    cin >>choice;
    return choice;
}
    int get_choice(struct line *p)
    {
    int i,choice;
    cout <<"\n...This is the start of your file so far...\n";
    for (i=1;p->next!=NULL;p=p->next,i++)
         cout <<i<<" "<<p->str<<endl;
         cout <<i<<" "<<p->str<<endl;
        cout <<"...This is the end"<<endl;

    cout <<"(Enter 1 to Insert,2 to Delete,and 3 to Quit)\n\t";
    cin >>choice;
    return choice;
    }
void add_line (struct line *p)
{
    struct line  *p_new, *p_start;
    char str_new[40];
    len++;
    p_start=p;
    p_new=(struct line *)malloc(sizeof(struct line));
    cout <<"First enter the line number and then its contens:\n";
     cout<<len<<":";
    fflush(stdin);
    cin.getline(str_new,40);
    fflush(stdin);
    for (;p->next!=NULL;p=p->next);

    if(len==1)
    {
        p->next=NULL;
        strcpy(p->str,str_new);
    }
    else
    {
        
        strcpy(p_new->str,str_new);
        p->next=p_new;
        p_new->next=NULL;
    }
    
      //return p_start;

}
----------------解决方案--------------------------------------------------------
支持一下
----------------解决方案--------------------------------------------------------
你两兄弟，不管如何，先谢了，等下回赖在测，上课去了，呵呵呵
----------------解决方案--------------------------------------------------------
你要小心空指针问题..而且指针是地址..其实即使你不用做参数..函数结束后空间还是会保留的..所以没必要用做参数..容易错..很难改正的
----------------解决方案--------------------------------------------------------