insert in Linked List Turbo C

问题

I am trying to program a text editor in C. I am having trouble with inserting an element in a linked list. The program simply won't insert anything in the middle of the linked list.

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

I used singly linked list.

struct node {
struct node *previous;
int c;
int x;
int y;
struct node *next;
}*head;

this works fine:

void characters(int typed, int xpos, int ypos)      //assign values of a node
{
struct node *temp,*var,*temp2;
temp=(struct node *)malloc(sizeof(struct node));
temp->c=typed;
temp->x=xpos;
temp->y=ypos;

if(head==NULL)
{
    head=temp;
    head->next=NULL;
}

else
{
    temp2=head;
    while(temp2!=NULL)
    {
        var=temp2;
        temp2=temp2->next;
    }
    temp2=temp;
    var->next=temp2;
    temp2->next=NULL;
}

}

this works just fine too.

void printer()                          //to print everything
{
struct node *temp;
temp=head;
while(temp!=NULL)
{
    gotoxy(temp->x,temp->y);
    printf("%c",temp->c);
    temp=temp->next;
}

}

this works just fine too:

void deletesEnd                  //delete at the end
{
struct node *temp,*last;
temp=head;
last=temp;
while(temp!=NULL && temp->next!=NULL)
{
    last=temp;
    temp=temp->next;
}
if(last==temp)
    {
        free(temp);
        head=NULL;
    }
else{
free(last->next);
last->next=NULL;
}
}

THIS IS THE PROBLEM:

 void checker(int ch, int xpos, int ypos)
{
int flag=0;
struct node *temp,*temp1,*insert_node;
temp=head;
while(temp!=NULL)
{
    if(temp->x==xpos && temp->y==ypos)
    {
        temp1=temp;
        temp=insert_node;
        insert_node->c=ch;
        insert_node->x=xpos;
        insert_node->y=ypos;
        insert_node->next=temp1;
        flag=1;
        break;
    }

    else
        temp= temp->next;
}
free(temp);
free(temp1);
if(flag==0)
    characters(ch,xpos,ypos);
}

main()
{
int c;                          //for storing the character
int x,y;                    //for the position of the character
clrscr();
for(;;)
{
    c=getch();
    x=wherex();
    y=wherey();
    if(c==27)
        exit(0);

    else if(c==0|| c==224)
    {
        switch(getch())
        {
            case 72:                    //for up
                    gotoxy(x,y-1);
                    break;
            case 80:                    //for down
                    gotoxy(x,y+1);
                    break;
            case 75:                    //for left
                    gotoxy(x-1,y);
                    break;
            case 77:                    //for right
                    gotoxy(x+1,y);
                    break;
         }
    }

    else if(c==13)
    {
        printf("\n");
    }

    else if(c==8)                       //for backspace
    {
            deletesEnd();
            clrscr();
            printer();

    }

    else                        //for normal characters
    {
        checker(c,x,y);
           //   characters(c,x,y);
        printer();
    }
}
}

I tried to debug it, it goes inside the loop with the conditional statement of ((temp->x==xpos && temp->y==ypos)) Thus, the program is supposed to insert an element but it doesn't. :(

回答1:

Maybe you have to malloc a struct node for the element you want to insert first, not just declare a struct node *.

Try to add struct node *insert_node = (struct node *)malloc(struct node) in your checker method.

回答2:

Try concept of insertion from this one - It can insert a node from front end

Just make a new pointer to node and name it create

struct node *create;

int item;
printf("Enter a number you want to insert\n\t");
scanf("%d",&item);
create = (struct node*)malloc(sizeof(struct node*));
create->info = item;
create->ptr = first;
HEAD = create;

来源：https://stackoverflow.com/questions/18042984/insert-in-linked-list-turbo-c

标签

linked-list