this is the error I got at the bottom:
#include <stdio.h>
// algorithm : use two pointers and they're n-1 nodes apart.
// when first reach the end, 2nd one reaches nth node.
typedef struct node {
struct node* next;
int data;
}node;
node* findnthnode( node *head, int n)
{
node *p1;
node *p2;
p1 = *p1->next->next;
// if head is null, return null
// if n > length of list, return null
// if n = 0, we return the tail.
// if there're two nodes,
// n=0, we return node2,
// n=1, we return node1(head)
// n>=2, we return NULL
// let p1 go n-1 steps
for (; n>0 && p1 ; n--){
p1 = p1->next;
}
if (!p1)
return NULL;
else
p2 = head;
// move p1, p2 together to traverse list
while (p1 && p1->next){
p1 = p1->next;
p2 = p2->next;
}
return p2;
}
int main()
{
// build a list
node a[3] = 0;
node *p;
int i;
a[0].data = 2;
a[0].next = &a[1];
a[1].data = 5;
a[1].next = &a[2];
a[2].data = 3;
a[2].next = NULL;
for (i=0;i<4;i++ ){
p = findnthnode( a, i);
if (p)
printf("found %dth node = %d\n",i, p->data);
else
printf("not found!\n");
}
return 0;
}
10.cpp: In function `node* findnthnode(node*, int)':
10.cpp:14: cannot convert `node' to `node*' in assignment
10.cpp: In function `int main()':
10.cpp:46: invalid initializer
--- On Mon, 10/27/08, peternilsson42 <[EMAIL PROTECTED]> wrote:
From: peternilsson42 <[EMAIL PROTECTED]>
Subject: [c-prog] Re: question about compiler warning
To: [email protected]
Date: Monday, October 27, 2008, 12:14 AM
frank zhu <frank.zhu.mingyu@ ...> wrote:
>
> Hi,
> I've coded a program to find the nth node from the end
> of the linked list.
> It works and get me the right result, but I am puzzled
> as why I get the compiler warnings at the following line,
> p1 = p1->next;
> findnthnode. c:28: warning: assignment from incompatible
> pointer type
<snip>
> #include <stdio.h>
> // algorithm : use two pointers and they're n-1 nodes
> apart. when first
> reach the end, 2nd one reaches nth node.
>
> typedef struct {
> struct node* next;
> int data;
> }node;
Here you declare an anonymous struct (i.e. a struct with
no tag name) containing a member of type struct node; and
you also create an alias for the anonymous struct called
node. Neither the anonymous struct, or its alias, has
the type struct node.
You probably meant...
typedef struct node { /* note the tag */
struct node* next;
int data;
} node;
> node* findnthnode( node *head, int n)
> {
> node *p1;
<snip>
> p1 = p1->next;
The 'next' member of the anonymous struct is a pointer
to a struct node, not a pointer to the anonymous struct.
Indeed, you never actually declare what a struct node
is.
C allows pointers to incomplete types.
The assignment is a constraint violation and conforming
compilers are required to issue a diagnostic. However,
you appear to have your 'buzz' level so low that it's
not reported as an error.
Try p1 = p1->next->next and see how far your compiler
gets!
This is one of the reasons why many C programmers won't
do the typedef. Instead they simply use struct node
throughout.
--
Peter
[Non-text portions of this message have been removed]
