I'm getting parse errors in my code. I'm probably missing something silly.. but after staring at it, I can't figure out what's wrong. The errors start at line 26:
BinaryTree.cpp:26: parse error before 'new
BinaryTree.cpp:31: parse error before ';'
....etc etc... any ideas?
#include <cstdlib>
#include <iostream>
using namespace std;
class BinaryTree{
struct node{
int data;
node *left;
node *right;
};
node *root;
public:
BinaryTree(int);
void addNode(int);
void inorder();
void printInorder(node);
int getHeight();
int height(node);
};
BinaryTree::BinaryTree(int data){
node *new = new node;
new->data = data;
new->left = NULL;
new->right = NULL;
root = new;
}
void BinaryTree::addNode(int data){
node *new = new node;
new->data = data;
new->left = NULL;
new->right = NULL;
node *current;
node *parent = NULL;
current = root;
while(current){
parent = current;
if(new->data > current->data) current = current->right;
else current = current->left;
}
if(new->data < parent->data) parent->left = new;
else parent->right = new;
}
void BinaryTree::inorder()
printInorder(root);
}
void BinaryTree::printInorder(node current){
if(current != NULL){
if(tree->left) printInorder(tree->left);
cout<<" "<<tree->data<<" ";
if(tree->right) printInorder(tree->right);
}
else return;
}
int BinaryTree::getHeight(){
return height(root);
}
int BinaryTree::height(node new){
if (new == NULL) return 0;
else return max(height(new->left), height(new->right)) + 1;
}
int main(int argCount, char *argVal[]){
int number = atoi(argVal[1]);
BinaryTree myTree = new BinaryTree(number);
for(int i=2; i <= argCount; i++){
number = atoi(argVal[i]);
myTree.addNode(number);
}
myTree.inorder();
int height = myTree.getHeight();
cout << endl << "height = " << height << endl;
return 0;
}
new is a C++ keyword. You mustn't use it as an identifier (e.g. variable name).
In any event, your constructor would be better off as:
BinaryTree::BinaryTree(int data) : root(new node) { /* ... */ }
And your class as a whole would probably be better off with unique_ptr<Node>s.
new is keyword in c++ and You can't name variable with that word so
node *new = new node;
is illegal
new is a reserved word, you cannot use it as a variable name.
Related
I am working on a BST and when I print out the elements in any order, I get a random '0' appended to it, but I cannot find where its coming from.
I followed the pseudo code thats present in Introduction to algorithms by Cormen and have also looked at Geeks for Geeks but I have no luck getting rid of that 0.
#include <iostream>
using namespace std;
class Node {
public:
int data;
Node* LeftChild;
Node* RightChild;
Node(int data){
this->data = data;
this->LeftChild = NULL;
this->RightChild = NULL;
}
//pointers of the class
};
class BST {
private:
Node* root;
public:
BST(){ ///creating an empty tree in Constant Time
root = new Node(NULL);
}
Node* getRoot(){ return this->root; };
int i =0;
void printTree(Node *root)
{
if (root == NULL)
return;
else {
printTree(root->LeftChild);
cout << root->data << " ";
printTree(root->RightChild);
}
}
Node* InsertNode(Node *root,int data)
{
Node *z = new Node(data);
Node *y = new Node(NULL);
Node *x = this->root;
//if(x->data < z->data){
// x = z;
//return x;
//}
while(x!= NULL){
y = x;
if(data < x->data){
x = x->LeftChild;
}
else{
x = x->RightChild;
}
}
if(y== NULL) y= z;
else if(data < y->data){
y->LeftChild = z;
}
else{
y->RightChild =z;
}
return y;
/*
if(this->root->data== NULL){
this->root =z;
return root;
}
else{
this->root =y;
}
*/
//this->root = z;
//return root;
}
bool FindNode(Node *root,int data);
int Largest(Node *root){
return root->data;
}
};
int main()
{
BST myBst;
Node * root = (myBst.getRoot());
root = myBst.InsertNode(root, 24);
myBst.InsertNode(root, 60);
myBst.InsertNode(root, 55);
myBst.InsertNode(root, 32);
myBst.printTree(root);
return 0;
}
Here is the output:
0, 24,32,55,60
The constructor does not make a sense
BST(){ ///creating an empty tree in Constant Time
root = new Node(NULL);
}
There is created a dummy node with initialization of the data member data with NULL.
What you need is just to write
BST() : root( nullptr ) { ///creating an empty tree in Constant Time
}
The function InsertNode must have only one parameter instead of two parameters as you wrote
Node* InsertNode(Node *root,int data){
The pointer root is the data member of the class. So there is no need to pass it to the function. Otherwise the function should be declared as a static member function of the class (that nevertheless does not make a great sense).
That is the function should be declared like
void InsertNode( int data ){
Also the function has at least a memory leak
Node* InsertNode(Node *root,int data){
Node *z = new Node(data);
Node *y = new Node(NULL);
Node *x = this->root;
while(x!= NULL){
y = x;
//...
The function can be written for example the following way
void InsertNode( int data )
{
Node *new_node = Node( data );
Node **current = &root;
while ( *current != nullptr )
{
if ( data < ( *current )->data )
{
current = &( *current )->LeftChild;
}
else
{
current = &( *current )->RightChild;
}
}
*current = new_node;
}
Hello fellow programmers, the below code gives segmentation fault. This code aims to insert an element at the end of a linked list. I tried using print statements to debug it. I think the error is in passing the linked list pointer to insert() function. Please tell me how can I correct it. Thanks in advance.
Below is the code:
#include <iostream>
using namespace std;
class node {
public:
int data;
node *next;
node(int data) {
this->data = data;
this->next = NULL;
}
};
class linked_list {
public:
node *head;
linked_list() {
this->head = NULL;
}
};
void insert(node **head, int data);
void print(linked_list *L);
int main() {
int N;
linked_list *A = new linked_list();
cout << "N: ";
cin >> N;
for(int i=0; i<=N-1; i++) {
int t;
cin >> t;
insert(&(A->head), t);
}
print(A);
return 0;
}
void insert(node **head, int data) {
node *temp = new node(data);
if(*head == NULL) {
*head = temp;
return;
} else {
node *t = *head;
while(t->next != NULL) {
t=t->next;
}
t->next = temp;
return;
}
}
void print(linked_list *L) {
node * t = L->head;
while(t!=NULL) {
cout << t->data << " ";
t = t->next;
}
return;
}
main.cpp:42:14: error: using the result of an assignment as a
condition without parentheses [-Werror,-Wparentheses]
if(*head = NULL) {
~~~~~~^~~~~~
main.cpp:42:14: note: place parentheses around the assignment to
silence this warning
if(*head = NULL) {
^
( )
main.cpp:42:14: note: use '==' to turn this assignment into an
equality comparison
if(*head = NULL) {
^
==
1 error generated.
You're using assignment where you intended to do a comparison.
I am trying to implement the a dot product calculation formula into the linked list implementation on my below code and I am having the below error:
request for member 'add_node' in 'B', which is of pointer type 'linked_list {aka node*}' (maybe you meant to use '->' ?)
How can I clear that and make working code? I don't want to use classes as well
#include <iostream>
#include <stdlib.h>
using namespace std;
struct node
{
int data;
int index;
node *next;
};
typedef node* linked_list;
node *head = NULL;
node *tail = NULL;
void add_node(int i,int n)
{
node *tmp = new node;
tmp->index = i;
tmp->data = n;
tmp->next = NULL;
if(head == NULL)
{
head = tmp;
tail = tmp;
}
else
{
tail->next = tmp;
tail = tail->next;
}
}
void display(node *head)
{
while(head!=0)
{
cout << head->index <<" ," << head->data << endl;
display(head->next);
break;
}
}
int main()
{
linked_list A;
A.add_node(2,7);
A.add_node(4,5);
A.add_node(7,8);
A.add_node(9,4);
linked_list B;
B.add_node(3,5);
B.add_node(4,6);
B.add_node(9,5);
int product=0;
while(A!=0 && B!=0)
{
if(A->index == B->index)
{
product = product + A->data * B->data;
A=A->next;
B=B->next;
}
else if(A->index < B->index)
{
A=A->next;
}
else
{
B=B->next;
}
}
return product;
return 0;
}
The error tells you what you need to know. linked_list is a pointer. You need to use the -> operator, not the dot operator.
Additionally, your node struct does not contain a method called add_node(). In fact it doesn't contain any methods at all.
#include <iostream>
using namespace std;
struct node
{
int data;
int index;
node *next;
};
class linked_list
{
private:
node *head,*tail;
public:
linked_list()
{
head = NULL;
tail = NULL;
}
void add_node(int i,int n)
{
node *tmp = new node;
tmp->index = i;
tmp->data = n;
tmp->next = NULL;
if(head == NULL)
{
head = tmp;
tail = tmp;
}
else
{
tail->next = tmp;
tail = tail->next;
}
}
node* gethead()
{
return head;
}
};
void display(node *head)
{
while(head!=0)
{
cout << head->index <<" ," << head->data << endl;
display(head->next);
break;
}
}
int main()
{
linked_list A;
A.add_node(2,7);
A.add_node(4,5);
A.add_node(7,8);
A.add_node(9,4);
linked_list B;
B.add_node(3,5);
B.add_node(4,6);
B.add_node(9,5);
display(A.gethead());
display(B.gethead());
int product=0;
node *current_a = A.gethead();
node *current_b = B.gethead();
while(current_a != 0 && current_b!=0)
{
if(current_a->index == current_b->index)
{
product = product + current_a->data * current_b->data;
current_a=current_a->next;
current_b=current_b->next;
}
else if(current_a->index < current_b->index)
{
current_a=current_a->next;
}
else
{
current_b=current_b->next;
}
}
cout<<"\nDot Product : "<< product<<endl;
return 0;
}
enter code here
I am trying to implement a priority Queue by using a linked list in c++. However, when I run the program it triggers a breakpoint within "priorityQLinkedList::dequeue()" method. Can someone tell why this is the case and give me suggestions on how to fix it?
Code:
#include <iostream>
#include <cstring>
#include <iomanip>
using namespace std;
struct DAT
{
int id;
char fullname[50];
double savings;
};
struct NODE
{
DAT data;
NODE *N;
NODE *P;
NODE(const int i, const char *f, const double s)
{
data.id = i;
strcpy_s(data.fullname, f);
data.savings = s;
N = NULL;
P = NULL;
}
};
class priorityQLinkedList
{
private:
NODE *front;
NODE *back;
public:
priorityQLinkedList() { front = NULL; back = NULL; }
~priorityQLinkedList() { destroyList(); }
void enqueue(NODE *);
NODE* dequeue();
void destroyList();
};
void priorityQLinkedList::enqueue(NODE *n)
{
if (front == NULL) {
front = n;
back = n;
}
else {
NODE *temp = front;
if (n->data.id > temp->data.id)
{
front->P = n;
n->N = front;
front = n;
}
else
{
//search for the posistion for the new node.
while (n->data.id < temp->data.id)
{
if (temp->N == NULL) {
break;
}
temp = temp->N;
}
//New node id's smallest then all others
if (temp->N == NULL && n->data.id < temp->data.id)
{
back->N = n;
n->P = back;
back = n;
}
//New node id's is in the medium range.
else {
temp->P->N = n;
n->P = temp->P;
n->N = temp;
temp->P = n;
}
}
}
}
NODE* priorityQLinkedList::dequeue()
{
NODE *temp;
//no nodes
if (back == NULL) {
return NULL;
}
//there is only one node
else if (back->P == NULL) {
NODE *temp2 = back;
temp = temp2;
front = NULL;
back = NULL;
delete temp2;
return temp;
}
//there are more than one node
else {
NODE *temp2 = back;
temp = temp2;
back = back->P;
back->N = NULL;
delete temp2;
return temp;
}
}
void priorityQLinkedList::destroyList()
{
while (front != NULL) {
NODE *temp = front;
front = front->N;
delete temp;
}
}
void disp(NODE *m) {
if (m == NULL) {
cout << "\nQueue is Empty!!!" << endl;
}
else {
cout << "\nID No. : " << m->data.id;
cout << "\nFull Name : " << m->data.fullname;
cout << "\nSalary : " << setprecision(15) << m->data.savings << endl;
}
}
int main() {
priorityQLinkedList *Queue = new priorityQLinkedList();
NODE No1(101, "Qasim Imtiaz", 567000.0000);
NODE No2(102, "Hamad Ahmed", 360200.0000);
NODE No3(103, "Fahad Ahmed", 726000.0000);
NODE No4(104, "Usmaan Arif", 689000.0000);
Queue->enqueue(&No4);
Queue->enqueue(&No3);
Queue->enqueue(&No1);
Queue->enqueue(&No2);
disp(Queue->dequeue());
disp(Queue->dequeue());
disp(Queue->dequeue());
disp(Queue->dequeue());
disp(Queue->dequeue());
delete Queue;
return 0;
}
One problem which stands out in your dequeue() method is that you are calling delete on a NODE pointer, and then attempting to return this deleted pointer to the caller. This could cause an error either in dequeue() itself, or certainly in the caller who thinks he is getting back a pointer to an actual live NODE object.
One potential fix would be to create a copy of the NODE being dequeued. You would still remove the target from your list, but the caller would then be returned a valid pointer, which he could free later.
NODE* priorityQLinkedList::dequeue()
{
NODE *temp;
// no nodes
if (back == NULL) {
return NULL;
}
NODE *temp2 = back;
temp = new NODE(temp2->data.id, temp2->data.fullname, temp2->data.savings);
// there is only one node
else if (back->P == NULL) {
front = NULL;
back = NULL;
delete temp2;
return temp;
}
// there are more than one node
else {
back = back->P;
back->N = NULL;
delete temp2;
return temp;
}
}
You're deleting pointers in dequeue that priorityQLinkedList does not own, so you don't know if it is safe to delete them.
In this case, they are not since the node pointers passed to enqueue are addresses of local, stacked based variables and have not been allocated by new. (There's also the already mentioned problem of deleting a pointer then returning it, which is Undefined Behavior.)
The fix for the code as shown is to remove the calls to delete in dequeue. However, if changes are made so that the nodes passed to enqueue are dynamically allocated, you'll need to add something to handle that.
1.First change strcpy_s to strcpy is struct NODE.
2.Instead of Delete(temp2) use temp2--.
//no nodes
if (back == NULL) {
return NULL;
}
//there is only one node
else if (back->P == NULL) {
NODE *temp2 = back;
temp = temp2;
front = NULL;
back = NULL;
temp2--;
return temp;
}
//there are more than one node
else {
NODE *temp2 = back;
temp = temp2;
back = back->P;
back->N = NULL;
temp2--;
return temp;
}
I hope this will resolve the problem.
I am trying to build my own implementation of a linked list in C++. My code is compiling but apparently there is some issue with my pointers referring to invalid memory addresses.
Here is my implementation:
#include <iostream>
#include <string>
using namespace std;
class Node
{
private:
string _car;
Node* nextNode;
public:
void setCar(string car)
{
_car = car;
}
string getCar()
{
return _car;
}
void setNextNode(Node* node)
{
nextNode = node;
}
Node* getNextNode()
{
return nextNode;
}
};
Node* findLast(Node* node)
{
Node* nodeOut = NULL;
while (node->getNextNode() != NULL)
{
nodeOut = node->getNextNode();
}
return nodeOut;
}
string toString(Node* node)
{
string output = "";
while (node->getNextNode() != NULL)
{
output += node->getCar() + " ";
node = node->getNextNode();
}
return output;
}
int main()
{
char xit;
//ser head node to NULL
Node* headNode = NULL;
//create node 1
Node* node1 = new Node();
node1->setCar("Mercedes");
//create node 2
Node* node2 = new Node();
node2->setCar("BMW");
//set node links
headNode->setNextNode(node1);
node1->setNextNode(node1);
node2->setNextNode(node2);
headNode = node1;
Node* lastNode = findLast(headNode);
lastNode->setNextNode(NULL);
cout << toString(headNode) << endl;
//pause console
cin >> xit;
}
You need to relook at your code.
headNode = node1;
This assignment should be done before accesing any member function of the instance headNode.
Intially you have assigned NULL to this pointer.
After creating node1 you are setting to headNode that is invalid instance. This is the cause of crash.
Be ensure with your objective and then try to implement do some rough work on paper , make some diagram that way you would be more clear that what you are exactly trying to achive.
why setNextNode ??? i don't undeerstand what you wanted to achieve. be clear first.
As per my undertanding this code should be implemented like below..
#include <iostream>
#include <string>
using namespace std;
class Node
{
private:
string _car;
Node* nextNode;
public:
void setCar(string car)
{
_car = car;
}
string getCar()
{
return _car;
}
void setNextNode(Node* node)
{
nextNode = node;
}
Node* getNextNode()
{
return nextNode;
}
};
Node* findLast(Node* node)
{
Node* nodeOut = node->getNextNode();
while ( nodeOut->getNextNode()!= NULL)
{
nodeOut = nodeOut->getNextNode();
}
return nodeOut;
}
string toString(Node* node)
{
string output = "";
while (node != NULL)
{
output += node->getCar() + " ";
node = node->getNextNode();
}
return output;
}
int main()
{
char xit;
//ser head node to NULL
Node* headNode = NULL;
//create node 1
Node* node1 = new Node();
node1->setCar("Mercedes");
node1->setNextNode(NULL);//Make null to each next node pointer
headNode = node1; //assign the node1 as headNode
//create node 2
Node* node2 = new Node();
node2->setCar("BMW");
node2->setNextNode(NULL);
//set node links
node1->setNextNode(node2);
Node* lastNode = findLast(headNode);
lastNode->setNextNode(NULL);
cout << toString(headNode) << endl;
//pause console
cin >> xit;
}
Hope it would be useful for the beginner who implement ing the linklist in c++.
Reread this:
node1->setNextNode(node1);
node2->setNextNode(node2);
...and think about what you're doing here.
If you're going to write linked-list code, I'd advise at least looking at the interface for std::list. Right now, you're interface is at such a low level that you'd be at least as well off just manipulating pointers directly.
The cause of your actual error is:
headNode->setNextNode(node1);
headNode is still set to NULL, thus you're dereferencing a NULL pointer. As noted by Jerry, you're also calling having nodes point to themselves, which is not what you want.
It would be cleaner if you took the car as a constructor parameter.
When you allocate a new Node, the pointer nextNode is not initialized, it's just random junk. You will need to explicitly set it to NULL (probably in a constructor for Node).
Also, I assume you know that the standard C++ library has a linked list built in and you're just doing this for learning ;-)
Thanks for all the suggestions, here is my final code after major cleanup:
// LinkedListProject.cpp : main project file.
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace System;
using namespace std;
class Node
{
public:
Node()
:_car(""), _nextNode(NULL)
{
}
void SetCar(string car)
{
_car = car;
}
string GetCar()
{
return _car;
}
void SetNextNode(Node *node)
{
_nextNode = node;
}
Node * GetNextNode()
{
return _nextNode;
}
private:
string _car;
Node *_nextNode;
};
string GetData();
Node * AddNode(Node *firstNode, Node *newNode);
Node * DeleteNode(Node *firstNode, string nodeData);
void PrintNodes(Node *firstNode);
int main(int argc, char *argv[])
{
string command = "";
string data = "";
Node *firstNode = NULL;
do
{
cout << "Enter command: ";
cin >> command;
if(command == "add")
{
data = GetData();
Node *newNode = new Node();
newNode->SetCar(data);
firstNode = AddNode(firstNode, newNode);
}
else if(command == "delete")
{
data = GetData();
firstNode = DeleteNode(firstNode, data);
}
else if(command == "print")
{
PrintNodes(firstNode);
}
} while(command != "stop");
return 0;
}
string GetData()
{
string data = "";
cout << "Enter data: ";
cin >> data;
return data;
}
Node * AddNode(Node *firstNode, Node *newNode)
{
//add new node to front of queue
newNode->SetNextNode(firstNode);
firstNode = newNode;
return firstNode;
}
Node * DeleteNode(Node *firstNode, string nodeData)
{
Node *currentNode = firstNode;
Node *nodeToDelete = NULL;
if (firstNode != NULL)
{
//check first node
if(firstNode->GetCar() == nodeData)
{
nodeToDelete = firstNode;
firstNode = firstNode->GetNextNode();
}
else //check other nodes
{
while (currentNode->GetNextNode() != NULL &&
currentNode->GetNextNode()->GetCar() != nodeData)
{
currentNode = currentNode->GetNextNode();
}
if (currentNode->GetNextNode() != NULL &&
currentNode->GetNextNode()->GetCar() == nodeData)
{
nodeToDelete = currentNode->GetNextNode();
currentNode->SetNextNode(currentNode->GetNextNode()->GetNextNode());
}
}
if(nodeToDelete != NULL)
{
delete nodeToDelete;
}
}
return firstNode;
}
void PrintNodes(Node *firstNode)
{
Node *currentNode = firstNode;
while(currentNode != NULL)
{
cout << currentNode->GetCar() << endl;
currentNode = currentNode->GetNextNode();
}
}