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Operations on Queue

Tags : queue, geeksforgeeks, cpp, easy

Problem Statement - link #

Given a queue of integers and Q queries. The task is to perform operations on queue according to the query.

Queries are as:

  1. i x : (adds element x in the queue from rear).

  2. r : (Removes the front element of queue).

  3. h : (Returns the front element).

  4. f y : (check if the element y is present or not in the queue). Return “Yes” if present, else “No”

Your Task: Your task is to complete functions enqueue(), dequeue(), front() and find() which performs the operations described above in the problem description.

Expected Time Complexity: O(1) or enqueue(), dequeue() and front(); O(N) for find().
Expected Auxiliary Space: O(1)

Examples #

Example 1:

Input:
Q = 4
Queries = i 3 i 4 r f 3
Output: No
Explanation: Inserting 3 and 4 . When
we return and remove 3 and then when
we find 3 , it will return NO as
output as 3 is not present in the
queue.

Example 2:

Input:
Q = 6
Queries = i 2 i 4 i 3 i 5 h f 8
Output:
2
No
Explanation: Inserting 2, 4, 3, and 5
onto the queue: 2 4 3 5. h means front
So front is 2. f is find. 8 is not in
queue so No.

Constraints #

Solutions #

class Solution{
    public:
    
    //Function to push an element in queue.
    void enqueue(queue<int> &q,int x)
    {
       //Your code here
       q.push(x);
    }
     
    //Function to remove front element from queue.
    void dequeue(queue<int> &q)
    {
        //Your code here
        q.pop();
    }
    
    //Function to find the front element of queue.
    int front(queue<int> &q)
    {
        //Your code here
        return q.front();
    }
    
    //Function to find an element in the queue.
    string find(queue<int> q, int x)
    {
        //Your code here
        int n = q.size();
        for(int i=0; i<n; i++){
            int y = q.front(); q.pop();
            if(y==x) return "Yes";
        } 
        return "No";
    }
};