How store class objects in vector<vector<class *>> and access and pass them to function either by reference or value - c++

Question

#ifndef BINARY_TREE_H
#define BINARY_TREE_H
#include<iostream>
#include<vector>
using namespace std;
class Binary_Tree;
static int levelCount=0;
extern vector<vector<Binary_Tree*>> vec;
extern vector<Binary_Tree*> tempVec;
class Binary_Tree
{
public:
Binary_Tree()
{
childNum=0;
data=0;
level=0;
prev=NULL;
next[0]=NULL;
next[1]=NULL;
};
Binary_Tree(int d)
{
childNum=0;
data=d;
level=0;
prev=NULL;
next[0]=NULL;
next[1]=NULL;
levelCount++;
}
void insert_node(int,int,int);
int get_level();
int get_childCount();
friend int set_childNum(Binary_Tree*);
private:
int childNum;
int data;
int level;
Binary_Tree *prev;
Binary_Tree *next[2];
};
#endif // BINARY_TREE_H
Here is the implementation file
#include<iostream>
#include<cmath>
#include "Binary_Tree.h"
using namespace std;
void Binary_Tree::insert_node(int lev, int d, int sib)
{
if(vec.empty())
{
cout<<"You Have to create Root first";
}
else
{
if(set_childNum(vec[lev][sib-1])==0)
{
cout<<"Child cant be created parent Node already has two childs.";
}
else
{
childNum=set_childNum(vec[lev][sib-1]);
data=d;
level=lev+1;
prev=vec[lev][sib];
next[0]=NULL;
next[1]=NULL;
tempVec.clear();
for(int i=0; i<pow(2,(lev+1)); i++)
{
if(i==childNum-1)
{
tempVec.push_back(this);
}
else
tempVec.push_back(vec[lev][i]);
}
vector<vector<Binary_Tree*>>::iterator itr=vec.begin()+(lev+1);
vec.erase(itr);
vec.insert(itr,tempVec);
}
}
}
int set_childNum(Binary_Tree *lstNdAdr)
{
if(lstNdAdr->get_childCount()==0)
return 1;
else if(lstNdAdr->get_childCount()==1)
return 2;
else
return 0;
}
int Binary_Tree::get_level()
{
return level;
}
int Binary_Tree::get_childCount()
{
if(next[0]==NULL)
{
return 0;
}
else if(next[0]!=NULL && next[1]==NULL)
{
return 1;
}
else
{
return 2;
}
}
MAIN.cpp
#include <iostream>
#include<cmath>
#include"Binary_Tree.h"
using namespace std;
vector<vector<Binary_Tree*>> vec;
vector<Binary_Tree*> tempVec;
int main()
{
Binary_Tree tree;
here:
cout<<"Enter your Choice:1.Create Root Of Tree\n"
<<"2.Insert node\n"<<endl;
int choice;
cin>>choice;
switch(choice)
{
case 1:
{
int d;
cout<<"Enter Data to insert: ";
cin>>d;
Binary_Tree treeDummy(d);
tree=treeDummy;
tempVec.push_back(&tree);
vec.push_back(tempVec);
}
break;
case 2:
{
int lev;
int sibbling;
int d;
cout<<"Enter at which level and data and parent's sibling-no.: ";
cin>>lev;
cin>>d;
cin>>sibbling;
if(sibbling>pow(2,lev))
cout<<"Illegal Sibbling Number."<<endl;
else
tree.insert_node(lev,d,sibbling);
}
break;
}
int x;
cin>>x;
if(x==5)
{
cout<<endl<<endl;
goto here;
}
return 0;
}
in above code i am trying to create a binary tree type structure which can be manipulated and traversed dynamically that is any node can be inserted and can be removed at run time (although its incomplete because i am stuck at a problem). While pushing back the tempVec vector the code produces a segmentation fault and i am also doubtful in passing the object stored in vetcor> vec to the functions in the implementation (I am new to Stl and first time dealing with vector of vectors containing pointer to the class types)

Answer 1

The nested vector's entries are only filled if i is set to 1. But you attempt to access its element [0][0] regardless. You have out of bounds access when i is not 1.

Answer 2

There are numerous problems present in your code, that and combined with the poor style and formatting makes it not so fun to debug.
Binary_Tree treeDummy(d);
tree = treeDummy;
tempVec.push_back(&tree);
I'm not sure what you're trying to do here but the above looks wrong. You are shallow copying treeDummy's data over to tree. You'll lose the link to whatever child node tree points to. Afterwards you're pushing that same tree instance into your temporary vector. That means all the elements in your vector ends up pointing to the local variable tree in main. So even if no segfault occurred you would run into aliasing problems since they all refer to the same tree object and not a separate unique BinaryTree instance.
vector< vector<Binary_Tree*> >::iterator itr=vec.begin()+(lev+1);
vec.erase(itr);
vec.insert(itr,tempVec);
Your BinaryTree::insert_node is using an invalidated iterator after performing erase which is undefined behavior.
childNum = set_childNum(vec[lev][sib-1]);
// ...
prev = vec[lev][sib];
The above can access an out-of-bound index in your vector. eg. You push_back a tempVec with only 1 element in it and then call insert_node with sib = 1.
// ...
if(x == 5)
{
cout<<endl<<endl;
goto here;
}
The use of goto is also completely unnecessary here and should be replaced with a traditional while loop that checks for condition != 5.
The higher level problem in your program, however, is that there's no clear constraints and invariants in its design. What assumptions and preconditions do each of those functions need to work? Why use vectors to hold BinaryTree nodes when the class itself should be dealing with that. You should get the overall design sorted out first, otherwise you'll just play whack-a-mole as other bugs crop up.