17. Queue Operations

The problem can be found at the following link: Question Link

My Approach 1

To perform queue operations, I have implemented the following approach:

• For the insert() function, I simply push the given element (k) into the queue using the push() method.

• For the findFrequency() function, I iterate over all the elements in the queue. I compare each element with the given number (k) and count the occurrences.

• Finally, I return the frequency count (c).

Time Complexity

• The insert() function has a time complexity of O(1) since it performs a single operation to push an element into the queue.

• The findFrequency() function has a time complexity of O(n) since it iterates over all the elements in the queue to count the occurrences of k.

Code (C++)

class Solution{
public:
    void insert(queue<int> &q, int k){
        q.push(k);
    }
    
    int findFrequency(queue<int> &q, int k){
        int sz = q.size();
        int c = 0;
        while(sz--){
            if(q.front() == k)
                ++c;
            q.push(q.front());
            q.pop();
        }
        return c;
    }
};

My Approach 2

Alternatively, you can use a map or hash structure to store the frequency of each element in the queue. Here's the modified approach:

• Declare a map or unordered_map (hash) to store the frequency of each element in the queue.

• For the insert() function, increment the frequency of the given element (k) in the hash map and push the element into the queue using the push() method.

• For the findFrequency() function, return the frequency of the given number (k) from the hash map.

Time Complexity

• The insert() function has a time complexity of O(log n) since it requires inserting elements into the map, which takes logarithmic time complexity for balanced trees.

• The findFrequency() function has a time complexity of O(log n) since it performs a lookup operation in the map.

Code (C++)

class Solution{
public:
    map<int, int> hash;
    
    void insert(queue<int> &q, int k){
        ++hash[k];
        q.push(k);
    }
    
    int findFrequency(queue<int> &q, int k){
        return hash[k];
    }
};

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