Data Modelling & AI Data Structure & Algorithm

Ternary representation of Cantor set

23 June 2025

0

Given three integers A, B and L, the task is to print the ternary cantor set from range [A, B] upto L levels.
Ternary Cantor Set: A ternary Cantor set is a set built by removing the middle part of a line segment when divided into 3 parts and repeating this process with the remaining shorter segments. Below is an illustration of a cantor set.

An illustration of a Ternary Cantor Set

Examples:

Input: A = 0, B = 1, L = 2
Output:
Level 0: [0.000000] — [1.000000]
Level 1: [0.000000] — [0.333333] [0.666667] — [1.000000]
Level 2: [0.000000] — [0.111111] [0.222222] — [0.333333] [0.666667] — [0.777778] [0.888889] — [1.000000]
Explanation: For the given range [0, 1], in level 1, it is divided into three parts ([0, 0.33], [0.33, 0.67], [0.67, 1]). From the three parts, the middle part is ignored. This process is continued for every part in the subsequent executions.
Input: A = 0, B = 9, L = 3
Output:
Level_0: [0.000000] — [9.000000]
Level_1: [0.000000] — [3.000000] [6.000000] — [9.000000]
Level_2: [0.000000] — [1.000000] [2.000000] — [3.000000] [6.000000] — [7.000000] [8.000000] — [9.000000]
Level_3: [0.000000] — [0.333333] [0.666667] — [1.000000] [2.000000] — [2.333333] [2.666667] — [3.000000] [6.000000] — [6.333333] [6.666667] — [7.000000] [8.000000] — [8.333333] [8.666667] — [9.000000]

Approach:

Create a linked list data structure for each node of the Set, having the start value, end value and a pointer to the next node.
Initialize the list with the start and end value given as the input.
For the next level:
- Create a new node where the difference between the start and end values is $\frac{1}{3} rd$ of the initial, i.e. start value is $\frac{1}{3} rd$ less than the initial end value.
- Further, modify the original node, such that the end value is $\frac{1}{3} rd$ more of the initial start value.
- Place the pointer to the new node after the original one accordingly

Below is the implementation of the above approach:

C++

// C++ implementation to find the cantor set
// for n levels and
// for a given start_num and end_num
#include <bits/stdc++.h>
using namespace std;
 
// The Linked List Structure for the Cantor Set
typedef struct cantor {
    double start, end;
    struct cantor* next;
} Cantor;
 
// Function to initialize the Cantor Set List
Cantor* startList(Cantor* head,
                double start_num,
                double end_num)
{
    if (head == NULL) {
        head = new Cantor;
        head->start = start_num;
        head->end = end_num;
        head->next = NULL;
    }
    return head;
}
 
// Function to propagate the list
// by adding new nodes for the next levels
Cantor* propagate(Cantor* head)
{
    Cantor* temp = head;
 
    if (temp != NULL) {
        Cantor* newNode
            = new Cantor;
        double diff
            = (((temp->end) - (temp->start)) / 3);
 
        // Modifying the start and end values
        // for the next level
        newNode->end = temp->end;
        temp->end = ((temp->start) + diff);
        newNode->start = (newNode->end) - diff;
 
        // Changing the pointers
        // to the next node
        newNode->next = temp->next;
        temp->next = newNode;
 
        // Recursively call the function
        // to generate the Cantor Set
        // for the entire level
        propagate(temp->next->next);
    }
 
    return head;
}
 
// Function to print a level of the Set
void print(Cantor* temp)
{
    while (temp != NULL) {
        printf("[%lf] -- [%lf]\t",
            temp->start, temp->end);
        temp = temp->next;
    }
    cout << endl;
}
 
// Function to build and display
// the Cantor Set for each level
void buildCantorSet(int A, int B, int L)
{
    Cantor* head = NULL;
    head = startList(head, A, B);
    for (int i = 0; i < L; i++) {
        cout <<"Level_"<< i<<" : ";
        print(head);
        propagate(head);
    }
    cout <<"Level_"<< L<<" : ";
    print(head);
}
 
// Driver code
int main()
{
    int A = 0;
    int B = 9;
    int L = 2;
    buildCantorSet(A, B, L);
 
    return 0;
}
 
// This code is contributed by shivanisingh

C

// C implementation to find the cantor set
// for n levels and
// for a given start_num and end_num
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
// The Linked List Structure for the Cantor Set
typedef struct cantor {
    double start, end;
    struct cantor* next;
} Cantor;
 
// Function to initialize the Cantor Set List
Cantor* startList(Cantor* head,
                  double start_num,
                  double end_num)
{
    if (head == NULL) {
        head = (Cantor*)malloc(sizeof(Cantor));
        head->start = start_num;
        head->end = end_num;
        head->next = NULL;
    }
    return head;
}
 
// Function to propagate the list
// by adding new nodes for the next levels
Cantor* propagate(Cantor* head)
{
    Cantor* temp = head;
 
    if (temp != NULL) {
        Cantor* newNode
            = (Cantor*)malloc(sizeof(Cantor));
        double diff
            = (((temp->end) - (temp->start)) / 3);
 
        // Modifying the start and end values
        // for the next level
        newNode->end = temp->end;
        temp->end = ((temp->start) + diff);
        newNode->start = (newNode->end) - diff;
 
        // Changing the pointers
        // to the next node
        newNode->next = temp->next;
        temp->next = newNode;
 
        // Recursively call the function
        // to generate the Cantor Set
        // for the entire level
        propagate(temp->next->next);
    }
 
    return head;
}
 
// Function to print a level of the Set
void print(Cantor* temp)
{
    while (temp != NULL) {
        printf("[%lf] -- [%lf]\t",
               temp->start, temp->end);
        temp = temp->next;
    }
    printf("\n");
}
 
// Function to build and display
// the Cantor Set for each level
void buildCantorSet(int A, int B, int L)
{
    Cantor* head = NULL;
    head = startList(head, A, B);
    for (int i = 0; i < L; i++) {
        printf("Level_%d : ", i);
        print(head);
        propagate(head);
    }
    printf("Level_%d : ", L);
    print(head);
}
 
// Driver code
int main()
{
    int A = 0;
    int B = 9;
    int L = 2;
    buildCantorSet(A, B, L);
 
    return 0;
}

Java

// Java implementation to find the cantor set
// for n levels and
// for a given start_num and end_num
 
class GFG
{
 
    // The Linked List Structure for the Cantor Set
    static class Cantor
    {
        double start, end;
        Cantor next;
    };
 
    static Cantor Cantor;
 
    // Function to initialize the Cantor Set List
    static Cantor startList(Cantor head, double start_num, 
                            double end_num)
    {
        if (head == null) 
        {
            head = new Cantor();
            head.start = start_num;
            head.end = end_num;
            head.next = null;
        }
        return head;
    }
 
    // Function to propagate the list
    // by adding new nodes for the next levels
    static Cantor propagate(Cantor head) 
    {
        Cantor temp = head;
 
        if (temp != null)
        {
            Cantor newNode = new Cantor();
            double diff = (((temp.end) - (temp.start)) / 3);
 
            // Modifying the start and end values
            // for the next level
            newNode.end = temp.end;
            temp.end = ((temp.start) + diff);
            newNode.start = (newNode.end) - diff;
 
            // Changing the pointers
            // to the next node
            newNode.next = temp.next;
            temp.next = newNode;
 
            // Recursively call the function
            // to generate the Cantor Set
            // for the entire level
            propagate(temp.next.next);
        }
 
        return head;
    }
 
    // Function to print a level of the Set
    static void print(Cantor temp)
    {
        while (temp != null) 
        {
            System.out.printf("[%f] -- [%f]", temp.start, temp.end);
            temp = temp.next;
        }
        System.out.printf("\n");
    }
 
    // Function to build and display
    // the Cantor Set for each level
    static void buildCantorSet(int A, int B, int L)
    {
        Cantor head = null;
        head = startList(head, A, B);
        for (int i = 0; i < L; i++) 
        {
            System.out.printf("Level_%d : ", i);
            print(head);
            propagate(head);
        }
        System.out.printf("Level_%d : ", L);
        print(head);
    }
 
    // Driver code
    public static void main(String[] args) 
    {
        int A = 0;
        int B = 9;
        int L = 2;
        buildCantorSet(A, B, L);
    }
}
 
// This code is contributed by Rajput-Ji

Python3

# Python3 implementation to find the cantor set
# for n levels and
# for a given start_num and end_num
# The Linked List Structure for the Cantor Set
class Cantor:
 
    def __init__(self):
     
        self.start = 0;
        self.end = 0;
        self.next = None;
     
cantor = None;
 
# Function to initialize the Cantor Set List
def startList(head, start_num, end_num):
 
    if (head == None) :
     
        head = Cantor();
        head.start = start_num;
        head.end = end_num;
        head.next = None;
     
    return head;
 
# Function to propagate the list
# by adding new nodes for the next levels
def propagate(head):
 
    temp = head;
 
    if (temp != None):
     
        newNode = Cantor();
        diff = (((temp.end) - (temp.start)) / 3);
         
        # Modifying the start and end values
        # for the next level
        newNode.end = temp.end;
        temp.end = ((temp.start) + diff);
        newNode.start = (newNode.end) - diff;
         
        # Changing the pointers
        # to the next node
        newNode.next = temp.next;
        temp.next = newNode;
         
        # Recursively call the function
        # to generate the Cantor Set
        # for the entire level
        propagate(temp.next.next);
     
    return head;
 
# Function to Print a level of the Set
def Print(temp):
 
    while (temp != None) :
     
        print("[", temp.start, "] -- [", temp.end, "] ", sep = "", end = "");
        temp = temp.next;
     
    print()
 
# Function to build and display
# the Cantor Set for each level
def buildCantorSet(A, B, L):
 
    head = None;
    head = startList(head, A, B);
    for i in range(L):
     
        print("Level_", i, " : ", sep = "", end = "");
        Print(head);
        propagate(head);
     
    print("Level_", L, " : ", end = "", sep = "");
    Print(head);
 
# Driver code
A = 0;
B = 9;
L = 2;
buildCantorSet(A, B, L);
 
# This code is contributed by phasing17

C#

// C# implementation to find the cantor set
// for n levels and
// for a given start_num and end_num
using System;
 
class GFG
{
 
    // The Linked List Structure for the Cantor Set
    class Cantor
    {
        public double start, end;
        public Cantor next;
    };
 
    static Cantor cantor;
 
    // Function to initialize the Cantor Set List
    static Cantor startList(Cantor head, double start_num, 
                            double end_num)
    {
        if (head == null) 
        {
            head = new Cantor();
            head.start = start_num;
            head.end = end_num;
            head.next = null;
        }
        return head;
    }
 
    // Function to propagate the list
    // by adding new nodes for the next levels
    static Cantor propagate(Cantor head) 
    {
        Cantor temp = head;
 
        if (temp != null)
        {
            Cantor newNode = new Cantor();
            double diff = (((temp.end) - (temp.start)) / 3);
 
            // Modifying the start and end values
            // for the next level
            newNode.end = temp.end;
            temp.end = ((temp.start) + diff);
            newNode.start = (newNode.end) - diff;
 
            // Changing the pointers
            // to the next node
            newNode.next = temp.next;
            temp.next = newNode;
 
            // Recursively call the function
            // to generate the Cantor Set
            // for the entire level
            propagate(temp.next.next);
        }
 
        return head;
    }
 
    // Function to print a level of the Set
    static void print(Cantor temp)
    {
        while (temp != null) 
        {
            Console.Write("[{0:F6}] -- [{1:F6}]", 
                            temp.start, temp.end);
            temp = temp.next;
        }
        Console.Write("\n");
    }
 
    // Function to build and display
    // the Cantor Set for each level
    static void buildCantorSet(int A, int B, int L)
    {
        Cantor head = null;
        head = startList(head, A, B);
        for (int i = 0; i < L; i++) 
        {
            Console.Write("Level_{0} : ", i);
            print(head);
            propagate(head);
        }
        Console.Write("Level_{0} : ", L);
        print(head);
    }
 
    // Driver code
    public static void Main(String[] args) 
    {
        int A = 0;
        int B = 9;
        int L = 2;
        buildCantorSet(A, B, L);
    }
}
 
// This code is contributed by Rajput-Ji

Javascript

<script>
 
// Javascript implementation to find the cantor set
// for n levels and
// for a given start_num and end_num
// The Linked List Structure for the Cantor Set
class Cantor
{
    constructor()
    {
        this.start = 0;
        this.end = 0;
        this.next = null;
    }
};
 
var cantor = null;
 
// Function to initialize the Cantor Set List
function startList(head, start_num, end_num)
{
    if (head == null) 
    {
        head = new Cantor();
        head.start = start_num;
        head.end = end_num;
        head.next = null;
    }
    return head;
}
// Function to propagate the list
// by adding new nodes for the next levels
function propagate(head) 
{
    var temp = head;
 
    if (temp != null)
    {
        var newNode = new Cantor();
        var diff = (((temp.end) - (temp.start)) / 3);
        // Modifying the start and end values
        // for the next level
        newNode.end = temp.end;
        temp.end = ((temp.start) + diff);
        newNode.start = (newNode.end) - diff;
        // Changing the pointers
        // to the next node
        newNode.next = temp.next;
        temp.next = newNode;
        // Recursively call the function
        // to generate the Cantor Set
        // for the entire level
        propagate(temp.next.next);
    }
    return head;
}
// Function to print a level of the Set
function print(temp)
{
    while (temp != null) 
    {
        document.write("["+temp.start.toFixed(6)+"] -- ["+
        temp.end.toFixed(6)+"] ");
        temp = temp.next;
    }
    document.write("<br>");
}
// Function to build and display
// the Cantor Set for each level
function buildCantorSet(A, B, L)
{
    var head = null;
    head = startList(head, A, B);
    for (var i = 0; i < L; i++) 
    {
        document.write("Level_"+ i +" : ");
        print(head);
        propagate(head);
    }
    document.write("Level_"+ L +" : ");
    print(head);
}
// Driver code
var A = 0;
var B = 9;
var L = 2;
buildCantorSet(A, B, L);
 
 
</script>

Output:
Level_0 : [0.000000] — [9.000000]
Level_1 : [0.000000] — [3.000000] [6.000000] — [9.000000]
Level_2 : [0.000000] — [1.000000] [2.000000] — [3.000000] [6.000000] — [7.000000] [8.000000] — [9.000000]

References: Cantor Set Wikipedia
Related Article: N-th term of George Cantor set of rational numbers

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Ternary representation of Cantor set

C++

C

Java

Python3

C#

Javascript

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