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Control Flow

2 (2.2%)

Arrays, Strings, Pointers, and References

8 (9%)

Functions

4 (4.5%)

Basic object-oriented programming

30 (33.7%)

A bit more advanced OOP (Composition, Operator overloading, Inheritance, Virtual Functions)

18 (20.2%)

Templates

8 (9%)

Other (Explain)

4 (4.5%)

Working with files?  (Streams)

15 (16.9%)

Total Members Voted: 89

[ILikePie]

Tried messing around with those nodes just now, the correct syntax is this:

Code: [Select]

...
node a; a.value = 1;
node b; b.value = 0; b.left = &a;
node c; c.value = 0; c.left = &b;
printf("%d\n", c.left->left->value);
...

$ gcc -o nodes nodes.c
$ ./nodes
1


[Blank Expression]

That code only works if you're stack allocating your nodes. Which, in practice, you will never do.

[SolarShado]

That code only works if you're stack allocating your nodes. Which, in practice, you will never do.

True, but (aside from the malloc calls) the only change is upgrading the period to an arrow between 'c' and the first 'left' right?
Well... all the other periods... aaand dropping the ampersands on lines 2&3...

Ah, and add a star to the variable type.

So it becomes this

Code: [Select]

...
node* a, b, c;
/* 3 malloc calls */
a->value = 1;
 b->value = 0; b->left = a;
 c->value = 0; c->left = b;
printf("%d\n", c->left->left->value);
...

I think that's it... (still rather new to C, but I think i've got the syntax around pointers figured out)

[qwertyuiopas]

One pointer, it's not

Code: [Select]

node* a, b, c;
as that would have an entirely unexpected result. Try

Code: [Select]

node *a, *b, *c;
instead.


Edit: Why not give a full example?

This is only one of the countless ways to interact with a tree structure. This is only an example, so it's not really the qality of code that should be used in an actual project, but it should be sufficient for an example.

Spoiler: Somewhat long example (click to show/hide)

Code: [Select]


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

typedef struct Node
{
    struct Node *parent, *left, *right;
    unsigned int data;
} Node;

Node *AddLeftNode(Node *parent, unsigned int data)
{
    if(!parent || parent->left)
      return NULL;

    Node *new = malloc(sizeof(Node));
    if(!new)
      return NULL;

    new->left = NULL;
    new->right = NULL;
    new->parent = parent;
    new->data = data;
    parent->left = new;

    return new;
}

Node *AddRightNode(Node *parent, unsigned int data)
{
    if(!parent || parent->right)
      return NULL;

    Node *new = malloc(sizeof(Node));
    if(!new)
      return NULL;

    new->left = NULL;
    new->right = NULL;
    new->parent = parent;
    new->data = data;
    parent->right = new;

    return new;
}

Node *AddNode(Node *parent, unsigned int data)
{
    if(!parent || (parent->right && parent->left))
      return NULL;

    if(parent->right)
      return AddLeftNode(parent, data);
    else
      return AddRightNode(parent, data);
}

void RecursivelyPrint(Node *parent, unsigned int indent)
{
    if(!parent)
      return;

    int i;
    for(i = 0; i < indent; i++)
      printf(" ");

    printf("%d\n", parent->data);

    if(parent->right)
      RecursivelyPrint(parent->right, indent + 1);

    if(parent->left)
      RecursivelyPrint(parent->left, indent + 1);
}

int main(int argc, char *argv[])
{
    Node root = {NULL, NULL, NULL, 12345};

    if(!AddNode(&root, 6)) return 1;
    if(!AddNode(&root, 7)) return 1;
    if(!AddLeftNode(root.right, 8)) return 1;
    if(!AddRightNode(root.left, 9)) return 1;
    if(!AddNode(root.right->left, 10)) return 1;
    if(!AddNode(root.right->left, 11)) return 1;
    if(!AddNode(root.right->left->left, 13)) return 1;
    RecursivelyPrint(&root, 0);

    return 0;
}



[ILikePie]

You can call a struct and the typedeffed type by the same name? Cool, I thought it can mess things up.

[Rose]

actually, in C++, Typedef is redundant, and, as far as I know, mostly ignored.

[Siquo]

actually, in C++, Typedef is redundant, and, as far as I know, mostly ignored.

Ignoring it would be madness, but yes, it is redundant. But qwerty is doing C (as you can see by the mallocs), where it is necessary.

[ILikePie]

actually, in C++, Typedef is redundant, and, as far as I know, mostly ignored.

C doesn't have any of those fancy OOP features you get with C++.

[TolyK]

*removed due to potential programming language war*
Sorry

[Siquo]

*removed due to potential programming language war*

Don't even joke about that. We try to keep the language/compiler/platform wars to a minimum.

[TolyK]

***

Don't even joke about that. We try to keep the language/compiler/platform wars to a minimum.

sure thing.

[IHateOutside]

You may want to remove the post in quotes as well.

[Deadmeat1471]

I've been learning the basics of Java just out of interest. This is giving me some problems.

Spoiler (click to show/hide)

Code: [Select]

import java.util.Scanner;

{
public static void main(String[] args)


public class GradeBook
{


private String courseName;
public GradeBook(String name)
{
courseName = name;
}

public void setCourseName(String name)
{
courseName = name;
}

public String getCourseName()
{
return courseName;
}

public void displayMessage()
{
System.out.printf("Welcome to the grade book for\n%s!\n\n"),
getCourseName());
}
public void determineClassAverage()
{
Scanner input = new Scanner(System.in);
int total;
int gradeCounter;
int grade;
double average;

total = 0
gradeCounter = 0

System.out.print("Enter grade or -1 to quit: ");
grade = input.nextInt();

while(grade != -1)
{
total = total + grade;
gradeCounter = gradeCounter + 1;

System.out.print("Enter grade or -1 to quit: ");
grade = input.nextInt();

}

if (gradeCounter != 0);
{
average = (double) total / gradeCounter;

System.out.printf("\nTotal of the %d grades entered is %d\n",
gradeCounter, total);
System.out.printf("Class average is %.2f\n",
average);
}
else
System.out.println("No grades were entered");
}

}
}

Theres some problem with the main method. any ideas?

Exact error message:
java.lang.NoSuchMethodError: main
Exception in thread "main"

[TolyK]

^ Sorry I can't help, I know java as much as the back of my head.
*****
In other news:
What do you think of this?

[Deadmeat1471]

That looks pretty epic.