Implement Queue using Linked List

Problem Statement - link #

Implement a Queue using Linked List. A Query Q is of 2 Types

1. 1 x (a query of this type means pushing ‘x’ into the queue)
2. 2 (a query of this type means to pop an element from the queue and print the poped elemen

Your Task: Complete the function push() which takes an integer as input parameter and pop() which will remove and return an element(-1 if queue is empty).

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

Examples #

Example 1:

Input:
Q = 4
Queries = 1 2 2 2 1 3 
Output: 2 -1
Explanation: In the second testcase 
1 2 the queue will be {2}
2   poped element will be {2} then
    the queue will be empty. 
2   the queue is empty and hence -1
1 3 the queue will be {3}.

Example 2:

Input:
Q = 5
Queries = 1 2 1 3 2 1 4 2
Output: 2 3
Explanation: n the first testcase
1 2 the queue will be {2}
1 3 the queue will be {2 3}
2   poped element will be 2 the
    queue will be {3}
1 4 the queue will be {3 4}
2   poped element will be 3.

Constraints #

• 1 <= Q <= 100
• 1 <= x <= 100

Solutions #

//Function to push an element into the queue.
void MyQueue:: push(int x)
{
        // Your Code
    QueueNode* temp = new QueueNode(x);
    if(!front) { front=rear=temp; return; }
    rear->next = temp;
    rear = rear->next;
    
}

//Function to pop front element from the queue.
int MyQueue :: pop()
{
        // Your Code 
    int ele = -1;
    if(front) {
        ele = front->data;     
        if(!front->next) 
            front = rear = NULL;  
        else
            front = front->next;
    }
    return ele;
    
}