Problem with inserting Nodes at Binary trees

[Blondeamon]

Ok i'll try to be brief. As part of one of my essays i thought of
creating source code for implementation of a binary tree and its basic
functions.

My code is both from books,lecture notes and googling but for some
reason on the printing of the nodes using inOrder traversal only 2 or 3
nodes are being printed.

I will put my code here although i am sure that only few might actually
comprehend what it is about because this subject needs good knowledge of
all the tricks about inserting/deleting nodes from theory of Binary Trees.


Exercise: Create code for a binary tree.The program reads the size of
the tree N and then inserts N nodes with values between 1 and 30.000
into the tree.
You cant enter a node if it is not already on the tree,so you must
search if it exists before entering it.

Finally ,after having inserted all N nodes print them using InOrder
traversal.


Tips: My code works for the first 2 nodes...but doesnt print anything
else.And i will bust my head open if i wont figure out why.

I appreciate any help guys , this is a tough question and this is my
first time on this forum.
(seems very warm so far btw)








#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

//the struct which represents the node
struct tnode {
struct tnode *left, *right;
int key;
};


void InOrder( tnode *x )
{
if (x == 0) return;
InOrder(x->left);
cout << x->key << " ";
InOrder(x->right);
}


int main ()
{
srand((long)2004126);
tnode *root = 0;
int size, key2;
int flag;

cout << "\nPlease enter the size of the tree. N: ";
cin >> size;

for (int i = 0; i < size; i++) {
key2 = 1 + rand() % 30000; //creating random node key
between 1-30.000
tnode *p = root;
tnode *q = 0 ;
flag = 0;

//searching existing tree for node with that value

while((p != 0)&&(flag==0)) {
q = p;
if (p->key == key2) {
flag = 1; //node with that key already
exists -cant enter
} else if (p->key < key2) {
p = p->left; //case 1: key smaller than root
} else {
p = p->right; //case 2: key bigger than root
}
}


//creating new node with key2 as content
if (flag == 0) { //flag is 0 when that value didnt
already exist on the tree
tnode *z = new tnode;
z->key = key2;
z->left = 0;
z->right = 0; //creation of nw node that will
take key2 as its value
//and will have 2 NULL kids (left and right)

if (q == 0) {
root = z;
//case of empty tree
//case handling about where the new node will be put
} else if (key2 > q->key) {
q->right = z;
} else {
q->left = z;
}
}
}

//cout << "\nroot is : "<< root->key; //not needed
,just for checking

//the value of root
InOrder(root);
cout << endl;
cin >> size;
return 0;
}

 

[Nikos Chantziaras]

My code is both from books,lecture notes and googling

It's a bad idea to copy&paste code; write your own

I will put my code here although i am sure that only few might actually
comprehend what it is about because this subject needs good knowledge of
all the tricks about inserting/deleting nodes from theory of Binary Trees.

Well, just because you have problems with it doesn't mean you need a
Nobel prize in IT to grasp it It looks like a straightforward and
trivial tree to me with no "tricks" or optimizations involved.

Tips: My code works for the first 2 nodes...but doesnt print anything
else.And i will bust my head open if i wont figure out why.

I appreciate any help guys , this is a tough question and this is my
first time on this forum.
(seems very warm so far btw)

#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

//the struct which represents the node
struct tnode {
struct tnode *left, *right;
int key;
};


void InOrder( tnode *x )
{
if (x == 0) return;
InOrder(x->left);
cout << x->key << " ";
InOrder(x->right);
}


int main ()
{
srand((long)2004126);
tnode *root = 0;
int size, key2;
int flag;

cout << "\nPlease enter the size of the tree. N: ";
cin >> size;

for (int i = 0; i < size; i++) {
key2 = 1 + rand() % 30000; //creating random node key
between 1-30.000
tnode *p = root;
tnode *q = 0 ;
flag = 0;

//searching existing tree for node with that value

while((p != 0)&&(flag==0)) {
q = p;
if (p->key == key2) {
flag = 1; //node with that key already
exists -cant enter
} else if (p->key < key2) {
p = p->left; //case 1: key smaller than root

Wrong. It's *bigger*, not smaller. That is you must either use:

p->key > key2

or:

key2 < p->key

but *not* what you're currently doing:

p->key < key2