Check if Queue Elements are pairwise consecutive | Set-2

Last Updated : 27 Oct, 2022

Given a Queue of integers. The task is to check if consecutive elements in the queue are pairwise consecutive.

Examples:

Input: 1 2 5 6 9 10 Output: Yes  Input: 2 3 9 11 8 7 Output: No

Approach :

Take a variable n to store size of queue.
Push an element to the queue which acts as marker.
Now, If size of queue is odd, start popping a pair while n > 2. Also, while popping these pairs, check for their difference and decrease n by 2, if there difference is not equal to 1, set flag to false.
If size of queue is even, start popping a pair while n > 1. Also, while popping these pairs, check for their difference and decrease n by 2, if their difference is not equal to 1, set flag to false.
Finally, check flag, if it is true, it means elements in the queue are pairwise sorted, else not.

Below is the implementation of above approach:

C++

   // C++ program to check if successive
// pair of numbers in the queue are
// consecutive or not
#include <bits/stdc++.h>
using namespace std;
 
// Function to check if elements are
// pairwise consecutive in queue
bool pairWiseConsecutive(queue<int> q)
{
    // Fetching size of queue
    int n = q.size();
 
    // Pushing extra element to the queue
    // which acts as marker
    q.push(INT_MIN);
 
    // Result flag
    bool result = true;
 
    // If number of elements in the
    // queue is odd pop elements while
    // its size is greater than 2.
    // Else, pop elements while its
    // size is greater than 1
    if (n % 2 != 0) {
 
        while (n > 2) {
            int x = q.front();
            q.pop();
            q.push(x);
            n--;
 
            int y = q.front();
            q.pop();
            q.push(y);
            n--;
 
            if (abs(x - y) != 1) {
                result = false;
            }
        }
 
        // Popping the last element of queue
        // and pushing it again.
        // Also, popping the extra element
        // that we have pushed as marker
        q.push(q.front());
        q.pop();
        q.pop();
    }
 
    else {
        while (n > 1) {
            int x = q.front();
            q.pop();
            q.push(x);
            n--;
 
            int y = q.front();
            q.pop();
            q.push(y);
            n--;
 
            if (abs(x - y) != 1) {
                result = false;
            }
        }
 
        // popping the extra element that
        // we have pushed as marker
        q.pop();
    }
 
    return result;
}
 
// Driver program
int main()
{
    // Pushing elements into the queue
    queue<int> q;
    q.push(4);
    q.push(5);
    q.push(-2);
    q.push(-3);
    q.push(11);
    q.push(10);
    q.push(5);
    q.push(6);
    q.push(8);
 
    if (pairWiseConsecutive(q))
        cout << "Yes" << endl;
    else
        cout << "No" << endl;
 
    return 0;
}
 
  

Java

   import java.util.LinkedList;
import java.util.Queue;
 
// Java program to check if successive 
// pair of numbers in the queue are 
// consecutive or not 
public class GFG {
 
// Function to check if elements are 
// pairwise consecutive in queue 
    static boolean pairWiseConsecutive(Queue<Integer> q) {
        // Fetching size of queue 
        int n = q.size();
 
        // Pushing extra element to the queue 
        // which acts as marker 
        q.add(Integer.MAX_VALUE);
 
        // Result flag 
        boolean result = true;
 
        // If number of elements in the 
        // queue is odd pop elements while 
        // its size is greater than 2. 
        // Else, pop elements while its 
        // size is greater than 1 
        if (n % 2 != 0) {
 
            while (n > 2) {
                int x = q.peek();
                q.remove();
                q.add(x);
                n--;
 
                int y = q.peek();
                q.remove();
                q.add(y);
                n--;
 
                if (Math.abs(x - y) != 1) {
                    result = false;
                }
            }
 
            // Popping the last element of queue 
            // and pushing it again. 
            // Also, popping the extra element 
            // that we have pushed as marker 
            q.add(q.peek());
            q.remove();
            q.remove();
        } else {
            while (n > 1) {
                int x = q.peek();
                q.remove();
                q.add(x);
                n--;
 
                int y = q.peek();
                q.remove();
                q.add(y);
                n--;
 
                if (Math.abs(x - y) != 1) {
                    result = false;
                }
            }
 
            // popping the extra element that 
            // we have pushed as marker 
            q.remove();
        }
 
        return result;
    }
 
// Driver program 
    static public void main(String[] args) {
        // Pushing elements into the queue 
        Queue<Integer> q = new LinkedList<>();
        q.add(4);
        q.add(5);
        q.add(-2);
        q.add(-3);
        q.add(11);
        q.add(10);
        q.add(5);
        q.add(6);
        q.add(8);
 
        if (pairWiseConsecutive(q)) {
            System.out.println("Yes");
        } else {
            System.out.println("No");
        }
 
    }
}
// This code is contributed by Rajput-Ji
 
  

Python3

   # Python3 program to check if successive 
# pair of numbers in the queue are 
# consecutive or not 
import sys, queue
 
# Function to check if elements are 
# pairwise consecutive in queue 
def pairWiseConsecutive(q): 
     
    # Fetching size of queue 
    n = q.qsize() 
 
    # Pushing extra element to the
    # queue which acts as marker 
    q.put(-sys.maxsize); 
 
    # Result flag 
    result = bool(True) 
 
    # If number of elements in the 
    # queue is odd pop elements while 
    # its size is greater than 2. 
    # Else, pop elements while its 
    # size is greater than 1 
    if (n % 2 != 0):
        while (n > 2):
            x = q.queue[0]
            q.get() 
            q.put(x) 
            n -= 1
 
            y = q.queue[0] 
            q.get() 
            q.put(y) 
            n -= 1
 
            if (abs(x - y) != 1):
                result = bool(False)
 
        # Popping the last element of queue 
        # and pushing it again. 
        # Also, popping the extra element 
        # that we have pushed as marker 
        q.put(q.queue[0])
        q.get() 
        q.get() 
         
    else:
        while (n > 1): 
            x = q.queue[0] 
            q.get() 
            q.put(x) 
            n -= 1
 
            y = q.queue[0]  
            q.get() 
            q.put(y) 
            n -= 1
 
            if (abs(x - y) != 1): 
                result = bool(False)
     
        # popping the extra element that 
        # we have pushed as marker 
        q.get()
 
    return result
 
# Driver code
 
# Pushing elements into the queue 
q = queue.Queue() 
q.put(4) 
q.put(5) 
q.put(-2) 
q.put(-3) 
q.put(11) 
q.put(10) 
q.put(5) 
q.put(6) 
q.put(8) 
 
if (bool(pairWiseConsecutive(q))):
    print("Yes") 
else:
    print("No") 
 
# This code is contributed by divyeshrabadiya07
 
  

C#

   // C# program to check if successive 
// pair of numbers in the queue are 
// consecutive or not 
using System;
using System.Collections.Generic;
 
class GFG 
{ 
 
    // Function to check if elements are 
    // pairwise consecutive in queue 
    static Boolean pairWiseConsecutive(Queue<int> q) 
    { 
        // Fetching size of queue 
        int n = q.Count; 
 
        // Pushing extra element to the queue 
        // which acts as marker 
        q.Enqueue(int.MaxValue); 
 
        // Result flag 
        Boolean result = true; 
 
        // If number of elements in the 
        // queue is odd pop elements while 
        // its size is greater than 2. 
        // Else, pop elements while its 
        // size is greater than 1 
        if (n % 2 != 0) 
        { 
            while (n > 2) 
            { 
                int x = q.Peek(); 
                q.Dequeue(); 
                q.Enqueue(x); 
                n--; 
 
                int y = q.Peek(); 
                q.Dequeue(); 
                q.Enqueue(y); 
                n--; 
 
                if (Math.Abs(x - y) != 1) 
                { 
                    result = false; 
                } 
            } 
 
            // Popping the last element of queue 
            // and pushing it again. 
            // Also, popping the extra element 
            // that we have pushed as marker 
            q.Enqueue(q.Peek()); 
            q.Dequeue(); 
            q.Dequeue(); 
        } else
        { 
            while (n > 1) 
            { 
                int x = q.Peek(); 
                q.Dequeue(); 
                q.Enqueue(x); 
                n--; 
 
                int y = q.Peek(); 
                q.Dequeue(); 
                q.Enqueue(y); 
                n--; 
 
                if (Math.Abs(x - y) != 1) 
                { 
                    result = false; 
                } 
            } 
 
            // popping the extra element that 
            // we have pushed as marker 
            q.Dequeue(); 
        } 
 
        return result; 
    } 
 
    // Driver Code
    static public void Main(String[] args) 
    { 
        // Pushing elements into the queue 
        Queue<int> q = new Queue<int>(); 
        q.Enqueue(4); 
        q.Enqueue(5); 
        q.Enqueue(-2); 
        q.Enqueue(-3); 
        q.Enqueue(11); 
        q.Enqueue(10); 
        q.Enqueue(5); 
        q.Enqueue(6); 
        q.Enqueue(8); 
 
        if (pairWiseConsecutive(q)) 
        { 
            Console.WriteLine("Yes"); 
        } 
        else
        { 
            Console.WriteLine("No"); 
        } 
    } 
} 
 
// This code is contributed by Rajput-Ji
 
  

Javascript

   // Javascript program to check if successive
// pair of numbers in the queue are
// consecutive or not
 
 
// Function to check if elements are
// pairwise consecutive in queue
function pairWiseConsecutive(q) {
    // Fetching size of queue
    let n = q.length;
 
    // Pushing extra element to the queue
    // which acts as marker
    q.push(Number.MIN_VALUE);
 
    // Result flag
    let result = true;
 
    // If number of elements in the
    // queue is odd pop elements while
    // its size is greater than 2.
    // Else, pop elements while its
    // size is greater than 1
    if (n % 2 != 0) {
 
        while (n > 2) {
            let x = q[0];
            q.shift();
            q.push(x);
            n--;
 
            let y = q[0];
            q.shift();
            q.push(y);
            n--;
 
            if (Math.abs(x - y) != 1) {
                result = false;
            }
        }
 
        // Popping the last element of queue
        // and pushing it again.
        // Also, popping the extra element
        // that we have pushed as marker
        q.push(q[0]);
        q.shift();
        q.shift();
    }
 
    else {
        while (n > 1) {
            let x = q[0];
            q.shift();
            q.push(x);
            n--;
 
            let y = q[0];
            q.shift();
            q.push(y);
            n--;
 
            if (Math.abs(x - y) != 1) {
                result = false;
            }
        }
 
        // popping the extra element that
        // we have pushed as marker
        q.shift();
    }
 
    return result;
}
 
// Driver program
// Pushing elements into the queue
let q = [];
q.push(4);
q.push(5);
q.push(-2);
q.push(-3);
q.push(11);
q.push(10);
q.push(5);
q.push(6);
q.push(8);
 
if (pairWiseConsecutive(q))
    console.log("Yes");
else
    console.log("No");
     
// This code is contributed by adityamaharshi21
 
  

Output

Yes

Complexity Analysis:

Time Complexity: O(n)
Auxiliary Space: O(1)

Check if Queue Elements are pairwise consecutive

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Article Tags :

Practice Tags :

Check if Queue Elements are pairwise consecutive | Set-2

C++

Java

Python3

C#

Javascript

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