Check if Queue Elements are pairwise consecutive | Set-2
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; } |
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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 |
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C#
// C# rogram 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
{
// 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
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
Output:
Yes
Time Complexity: O(n)
Auxiliary Space: O(1)
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Improved By : Rajput-Ji
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