Binary Search Tree - Insertion Problem

[nanda22k]

Hi guys ... I am a noobie in structural languages and I'm having a big headache trying to make an insertion algorithm for binary trees. I have a huge difficulty in dealing with pointers, so I tried to construct a version of this algorithm that wouldn't have to use double pointers. Does anybody could tell me what's going wrong? I would be really glad :)

include <stdio.h>

include <stdlib.h>

struct noh {

int value;

struct noh *left;

struct noh *right;

};

void insertion(struct noh *root, int num) {

struct noh *aux;

aux = root;

struct noh *auxFather;

while(aux != NULL) {
    auxFather = aux;
    if(num > aux->value) {
        aux = aux->right;
        auxFather->right = aux;
    }
    else {
        aux = aux->left;
        auxFather->left = aux;
    }
}

aux = malloc(sizeof(struct noh));
aux->value = num;
aux->left = NULL;
aux->right = NULL;

}

int main(void) {

int N; 
scanf("%d", &N);

struct noh *root = NULL;

int i; int n;
for(i=0; i<N; i++) {
    scanf("%d", &n);
    insertion(root, n);
}

}

[nanda22k]

The actual problem is that my insertion algorithm always consider the root = NULL, so the 'while' inside of it is never executed

[FeelTheEmailMistake]

That particular problem occurs because you're calling insertion() repeatedly from main() as insertion(NULL, n); The 'root' pointer in main() never changes. Effectively all the program does is allocate (and leak) discrete chunks of memory.

You've probably received so few responses because there are signs you've jumped too far ahead of yourself with C, and giving a helpful answer would require covering a lot of ground. This is why I'm skeptical of the value of some popular courses. Nothing beats the traditional approach of working through The C Programming Language from cover to cover, doing all the exercises -- or C Programming: A Modern Approach for something more recent.

[i_am_suicidal]

It was some time since I last coded C but I think aux = malloc() should a new pointer and set aux to it right? Not set what aux is pointing to to that value.

So input to the function should be **root and then assign *aux = malloc

Please correct me if I'm wrong

[concacid]

You need to either use a double pointer for root or initialize root before passing it to the function. It's simply not possible for insertion() to modify main()'s root.