Check Contiguous 1s Sequence in Binary Linked List

Last Updated : 03 Dec, 2023

Given a binary linked list and integer K, the task is to check whether the binary linked list contains a contiguous sequence of 1s of K length.

Examples:

Input: 0 -> 1 -> 1 -> 1 -> 0 -> 1 -> 1 -> 0 -> 1 -> 1, K = 3
Output: True
Explanation: In the given binary linked list, there is a contiguous sequence of three 1s between the second and fourth nodes (1 -> 1 -> 1). Therefore, the output is return True.

Input: 0 -> 0 -> 1 -> 0 -> 1 -> 1 -> 1 -> 1 -> 0, K = 4
Output: True
Explanation: In the given binary linked list, there is a contiguous sequence of four 1s between the fifth and eight nodes (1 -> 1 -> 1). Therefore, the output is return True.

Input: 0 -> 1 -> 0 -> 0-> 0-> 1, K = 5
Output: False
Explanation: In the given binary linked list, there is no contiguous sequence of five 1s so the output is False.

Approach: To solve the problem follow the below idea:

To solve this problem idea is to iterating through the linked list and keeping track of a counter variable count that increments whenever a 1 is encountered and resets to 0 whenever a 0 is encountered.

Here is steps of above approach:

Initialize variable count to 0.
Traverse the linked list using a while loop. Inside the loop, we check whether the current node contains a 1 or a 0.
If the current node contains a 1, we increment a counter variable count by 1.
If the value of count becomes equal to K, it means we have found a contiguous sequence of 1s of length K, so we set the Boolean flag variable flag to true and break out of the loop.
the current node contains a 0, we reset the value of count to 0, since a contiguous sequence of 1s has been broken.
Finally, we return the value of flag, which indicates whether we found a contiguous sequence of 1s of length K in the linked list.

Below is the implementation of the above approach:

C++

// C++ code for the above approach:
#include <bits/stdc++.h>
using namespace std;

// Defining the structure of a node
// in a binary linked list
struct Node {
    int data;
    Node* next;
};

// Function to create a new node
Node* newNode(int data)
{
    Node* node = new Node();
    node->data = data;
    node->next = NULL;
    return node;
}

// Function to determine whether the
// given binary linked list contains a
// contiguous sequence of 1s of length K
bool containsContiguousSequence(Node* head, int K)
{

    // Initialize a counter for consecutive 1s
    int count = 0;

    // Initialize a flag to indicate if
    // the contiguous sequence is found
    bool flag = false;
    while (head) {

        // Increment the count if the current
        // node contains 1
        if (head->data == 1) {
            count++;
            if (count == K) {

                // Set the flag to true if the
                // contiguous sequence of
                // length K is found
                flag = true;

                // Exit the loop early since the
                // sequence has been found
                break;
            }
        }

        // Reset the count if the current
        // node contains 0
        else {
            count = 0;
        }

        // Move to the next node in the
        // linked list
        head = head->next;
    }

    // Return true if a contiguous sequence of
    // 1s of length K was found, otherwise
    // false
    return flag;
}

// Driver code
int main()
{

    // Creating a sample binary linked list
    Node* head = newNode(0);
    head->next = newNode(1);
    head->next->next = newNode(1);
    head->next->next->next = newNode(1);
    head->next->next->next->next = newNode(0);
    head->next->next->next->next->next = newNode(1);
    head->next->next->next->next->next->next = newNode(1);
    head->next->next->next->next->next->next->next
        = newNode(0);
    head->next->next->next->next->next->next->next->next
        = newNode(1);
    head->next->next->next->next->next->next->next->next
        ->next
        = newNode(1);

    bool result = containsContiguousSequence(head, 3);

    // Printing the result
    if (result) {
        cout << "True";
    }
    else {
        cout << "False";
    }
    return 0;
}

Java

// Defining the structure of a node in a binary linked list
class Node {
    int data;
    Node next;

    Node(int data) {
        this.data = data;
        this.next = null;
    }
}

public class Main {
    // Function to determine whether the given binary linked list contains
    // a contiguous sequence of 1s of length K
    public static boolean containsContiguousSequence(Node head, int K) {
        // Initialize a counter for consecutive 1s
        int count = 0;
        
        // Initialize a flag to indicate if the contiguous sequence is found
        boolean flag = false;
        
        while (head != null) {
            // Increment the count if the current node contains 1
            if (head.data == 1) {
                count++;
                if (count == K) {
                    // Set the flag to true if the contiguous sequence of length K is found
                    flag = true;
                    // Exit the loop early since the sequence has been found
                    break;
                }
            } else {
                // Reset the count if the current node contains 0
                count = 0;
            }
            
            // Move to the next node in the linked list
            head = head.next;
        }
        
        // Return true if a contiguous sequence of 1s of length K was found, otherwise false
        return flag;
    }

    public static void main(String[] args) {
        // Creating a sample binary linked list
        Node head = new Node(0);
        head.next = new Node(1);
        head.next.next = new Node(1);
        head.next.next.next = new Node(1);
        head.next.next.next.next = new Node(0);
        head.next.next.next.next.next = new Node(1);
        head.next.next.next.next.next.next = new Node(1);
        head.next.next.next.next.next.next.next = new Node(0);
        head.next.next.next.next.next.next.next.next = new Node(1);
        head.next.next.next.next.next.next.next.next.next = new Node(1);

        boolean result = containsContiguousSequence(head, 3);

        // Printing the result
        if (result) {
            System.out.println("True");
        } else {
            System.out.println("False");
        }
    }
}
//Contributed by Aditi Tyagi

Python3

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

def contains_contiguous_sequence(head, K):
    # Initialize a counter for consecutive 1s
    count = 0

    # Initialize a flag to indicate if the contiguous sequence is found
    flag = False
    while head:
        # Increment the count if the current node contains 1
        if head.data == 1:
            count += 1
            if count == K:
                # Set the flag to true if the contiguous sequence of
                # length K is found
                flag = True
                # Exit the loop early since the sequence has been found
                break
        else:
            # Reset the count if the current node contains 0
            count = 0

        # Move to the next node in the linked list
        head = head.next

    # Return True if a contiguous sequence of 1s of length K was found, otherwise False
    return flag

# Driver code
if __name__ == "__main__":
    # Creating a sample binary linked list
    head = Node(0)
    head.next = Node(1)
    head.next.next = Node(1)
    head.next.next.next = Node(1)
    head.next.next.next.next = Node(0)
    head.next.next.next.next.next = Node(1)
    head.next.next.next.next.next.next = Node(1)
    head.next.next.next.next.next.next.next = Node(0)
    head.next.next.next.next.next.next.next.next = Node(1)
    head.next.next.next.next.next.next.next.next.next = Node(1)

    result = contains_contiguous_sequence(head, 3)

    # Printing the result
    if result:
        print("True")
    else:
        print("False")

// C# Code

using System;

// Defining the structure of a node in a binary linked list
public class Node
{
    public int Data { get; set; }
    public Node Next { get; set; }

    public Node(int data)
    {
        Data = data;
        Next = null;
    }
}

public class GFG
{
    // Function to determine whether the given binary linked list contains
    // a contiguous sequence of 1s of length K
    public static bool ContainsContiguousSequence(Node head, int K)
    {
        // Initialize a counter for consecutive 1s
        int count = 0;

        // Initialize a flag to indicate if the contiguous sequence is found
        bool flag = false;

        while (head != null)
        {
            // Increment the count if the current node contains 1
            if (head.Data == 1)
            {
                count++;
                if (count == K)
                {
                    // Set the flag to true if the contiguous sequence of length K is found
                    flag = true;
                    // Exit the loop early since the sequence has been found
                    break;
                }
            }
            else
            {
                // Reset the count if the current node contains 0
                count = 0;
            }

            // Move to the next node in the linked list
            head = head.Next;
        }

        // Return true if a contiguous sequence of 1s of length K was found, otherwise false
        return flag;
    }

    public static void Main()
    {
        // Creating a sample binary linked list
        Node head = new Node(0);
        head.Next = new Node(1);
        head.Next.Next = new Node(1);
        head.Next.Next.Next = new Node(1);
        head.Next.Next.Next.Next = new Node(0);
        head.Next.Next.Next.Next.Next = new Node(1);
        head.Next.Next.Next.Next.Next.Next = new Node(1);
        head.Next.Next.Next.Next.Next.Next.Next = new Node(0);
        head.Next.Next.Next.Next.Next.Next.Next.Next = new Node(1);
        head.Next.Next.Next.Next.Next.Next.Next.Next.Next = new Node(1);

        bool result = ContainsContiguousSequence(head, 3);

        // Printing the result
        if (result)
        {
            Console.WriteLine("True");
        }
        else
        {
            Console.WriteLine("False");
        }
    }
}

// This code is contributed by guptapratik

JavaScript

// Definition of a node in a binary linked list
class Node {
    constructor(data) {
        this.data = data;
        this.next = null;
    }
}

// Function to determine whether the given binary linked list contains a contiguous sequence of 1s of length K
function containsContiguousSequence(head, K) {
    // Initialize a counter for consecutive 1s
    let count = 0;

    // Initialize a flag to indicate if the contiguous sequence is found
    let flag = false;

    while (head) {
        // Increment the count if the current node contains 1
        if (head.data === 1) {
            count++;
            if (count === K) {
                // Set the flag to true if the contiguous sequence of length K is found
                flag = true;
                // Exit the loop early since the sequence has been found
                break;
            }
        } else {
            // Reset the count if the current node contains 0
            count = 0;
        }

        // Move to the next node in the linked list
        head = head.next;
    }

    // Return true if a contiguous sequence of 1s of length K was found, otherwise false
    return flag;
}

// Main function
function main() {
    // Creating a sample binary linked list
    const head = new Node(0);
    head.next = new Node(1);
    head.next.next = new Node(1);
    head.next.next.next = new Node(1);
    head.next.next.next.next = new Node(0);
    head.next.next.next.next.next = new Node(1);
    head.next.next.next.next.next.next = new Node(1);
    head.next.next.next.next.next.next.next = new Node(0);
    head.next.next.next.next.next.next.next.next = new Node(1);
    head.next.next.next.next.next.next.next.next.next = new Node(1);

    const result = containsContiguousSequence(head, 3);

    // Printing the result
    console.log(result ? "True" : "False");
}

// Call the main function
main();

Output

True

Time Complexity: O(n), where n is the number of nodes in the linked list.
Auxiliary Space: O(1), since we are only using a constant amount of extra space to store the counter variable count and the Boolean flag variable flag.