Click here to Skip to main content
Click here to Skip to main content

Tagged as

Creating a Binary Search Tree (BST) using C++ Standard Template Library (STL) Vector

, 20 Jun 2013 CPOL
Rate this:
Please Sign up or sign in to vote.
BST Data Structure using vector and deque

Introduction

Whenever we create trees, we need to be careful about memory allocations and de-allocation. Just out of a requirement, I thought of trying C++ STL (vectors and deques) to create a small BST. This article is the obvious consequence of that thought.

Background

BSTs are one of the most widely used data structures. C is the preferred language, however with the advent of C++ especially with C++11, it seems to be interesting to use C++. However, nothing related to C++11 is used in this article and can be used by C++98 compilers.

Using the Code

To create a BST, we need a BST data structure. Traditional BST data structures contain pointer to left and right sub-tree. Since I’ll be using vector and not pointers, I'll use vector indexes as pointer to left and right sub-tree.

struct bst
{
    unsigned int data;
    int leftIdx;
    int rightIdx;
};

Now, I’ll write various functions used in creating the BST and its child nodes. The first function will be used to create a BST. It will initialize the data structure with incoming data and reset the left and right index with -1 (similar to making the pointers NULL).

void MakeNode(vector<struct> &v1, int aData)
{
    struct bst b1 = { aData, -1, -1 };
    v1.push_back(b1);
}

The functions below will set the left and right child of a node. While setting, it assigns the correct index of left and right child on to the root node:

void setleft(vector <struct>&v1, int currIndex, int aData)
{
    unsigned int leftIndex = v1.size();
    v1[currIndex].leftIdx = leftIndex;
    struct bst b1 = { aData, -1, -1 };
    v1.push_back(b1);
}

void setright(vector<struct> &v1, int currIndex, int aData)
{
    unsigned int rightIndex = v1.size();
    v1[currIndex].rightIdx = rightIndex;
    struct bst b1 = { aData, -1, -1 };
    v1.push_back(b1);
}

The function below will be used to insert the data into the BST. Simple traversal to all the nodes till we find the appropriate place to insert the elements and call left and right functions defined above.

void Insert(vector<struct bst> &v1, int aData)
{
    if(v1.size() == 0)
    {
        cout<<"Note is not made yet. MakeNode first..."<<endl;
        return;
    }
    unsigned int currentIdx = 0;
    while ( currentIdx < v1.size() )
    {
        if(aData <= v1[currentIdx].data)
        {
            if( v1[currentIdx].leftIdx == -1)
            {
                setleft(v1, currentIdx, aData);
                break;
            }
            else
                currentIdx = v1[currentIdx].leftIdx;
        }
        else
        {
            if(v1[currentIdx].rightIdx == -1)
            {
                setright(v1, currentIdx, aData);
                break;
            }
            else
                currentIdx = v1[currentIdx].rightIdx;
        }
    }
}

The code below will be used for traversing the BST in in-order, pre-order, and post-order. The index is used as a starting point.

void InTrav(vector <struct bst> &v1, unsigned int Idx)
{
    if(v1[Idx].leftIdx != -1)
        InTrav(v1,v1[Idx].leftIdx );
    cout<<v1[Idx].data<<endl;
    if( v1[Idx].rightIdx != -1)
        InTrav(v1, v1[Idx].rightIdx);
}

void PreTrav(vector <struct bst> &v1, unsigned int Idx)
{
    cout<<v1[Idx].data<<endl;
    if(v1[Idx].leftIdx != -1)
        PreTrav(v1,v1[Idx].leftIdx );
    if( v1[Idx].rightIdx != -1)
        PreTrav(v1, v1[Idx].rightIdx);
}
void PostTrav(vector <struct bst> &v1, unsigned int Idx)
{
    if(v1[Idx].leftIdx != -1)
        PostTrav(v1,v1[Idx].leftIdx );
    if( v1[Idx].rightIdx != -1)
        PostTrav(v1, v1[Idx].rightIdx);
    cout<<v1[Idx].data<<endl;
}

The main program can be a simple one, for example:

int main()
{
    vector <struct bst> v1;
    MakeNode(v1, 30);
    Insert(v1, 20);
    Insert(v1, 6);
    Insert(v1, 40);
    Insert(v1, 35);
    Insert(v1, 16);
    Insert(v1, 7);

    InTrav(v1, 0);
    PreTrav(v1,0);
    PostTrav(v1,0);
    return 0;
}

Points of Interest

  1. The same code can be used for STL deque also. I haven’t checked it for any other containers.
  2. The performance will be slow as compared to raw pointers unless some vector (STL) optimizations are done. I didn't try that.
  3. You can use it for small BST which you can delete in one shot without worrying about memory de-allocating.
  4. Deletion of an element in BST will be updated in the next post.

History

  • First post

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

Deepak Kumar Gupta
Architect
India India
I love programming and started (in 1995)even before I got some professional education on the same. Since then I've worked on IP network stack (written IPv6 stack and next generation TCP Stack), VoIP, IP Security (IKE / IPSec).
My preferred programming language is C++ and I always explore the ways to improve the A.I based systems using enhanced algorithms and data structures.

Comments and Discussions

 
SuggestionConverted code to template based OO implementation. [modified] PinprofessionalSharjith12-Jun-14 1:43 
GeneralRe: Converted code to template based OO implementation. PinmemberDeepak Kumar Gupta12-Jun-14 18:45 
GeneralMy vote of 5 PinprofessionalSharjith12-Jun-14 1:16 
GeneralRe: My vote of 5 PinmemberDeepak Kumar Gupta12-Jun-14 18:44 
NewsMy Vote Of 10+ Pinmemberxox_c0bra_xox17-Aug-13 16:25 
GeneralMy vote of 5 PinprofessionalMihai MOGA13-Jul-13 20:42 
GeneralMy vote of 2 Pinmemberkore3d23-Jun-13 7:51 
GeneralRe: My vote of 2 PinmemberDeepak Kumar Gupta23-Jun-13 20:12 
GeneralRe: My vote of 2 Pinmemberkore3d23-Jun-13 21:31 
GeneralRe: My vote of 2 PinmemberDeepak Kumar Gupta23-Jun-13 21:39 
Questionwhere is the source? Pinmembersisira20-Jun-13 9:26 
AnswerRe: where is the source? PinmemberDeepak Kumar Gupta20-Jun-13 19:17 
SuggestionVector Indexes are Never "int" PinmemberMttD17-Jun-13 12:52 
GeneralRe: Vector Indexes are Never "int" PinmemberDeepak Kumar Gupta17-Jun-13 19:14 
GeneralRe: Vector Indexes are Never "int" PinmemberMttD18-Jun-13 0:34 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Mobile
Web01 | 2.8.141022.1 | Last Updated 21 Jun 2013
Article Copyright 2013 by Deepak Kumar Gupta
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid