How to Find Mode of All Elements in a Deque in C++?

In C++, deque is a container provided by the STL library of C++ that allows insertion and deletion from both ends. The mode of a deque represents the element that appears most frequently in the container. In this article, we will learn how to find the mode of all elements in a deque in C++.

Example:

Input:
Deque = {1, 2, 3, 4, 5, 2, 2, 3, 4, 4, 4}

Output:
Mode of the deque is: 4

Finding the Mode of All Elements in a Deque in C++

To find the mode of all elements in a std::deque in C++, we can use a std::unordered_map to store the frequencies of each element, then iterate through the map to find the element with the highest frequency which will be the mode of all deque elements.

C++ Program to Find the Mode of All Elements in a Deque

The below example demonstrates how we can find the mode of all elements in a std::deque in C++.

C++

// C++ Program to Find the Mode of All Elements in a Deque

#include <iostream>
#include <deque>
#include <unordered_map>
#include <algorithm>
using namespace std;


int main() {
    // Initializing a deque
    deque<int> dq = {1, 2, 3, 4, 5, 2, 2, 3, 4, 4, 4};

    // Creating a map to store the count of each element
    unordered_map<int, int> mp;

    // Count the frequency of each element in the deque
    for (int num : dq) {
        mp[num]++;
    }

    // Initialize mode with the first element
    int mode = dq.front(); 
    // Initialize maxFrequency with 0
    int maxFrequency = 0;  
    
    // Find the element with greates frequency to get the mode of all elements in the deque
    for (auto pair : mp) {
        if (pair.second > maxFrequency) {
            maxFrequency = pair.second;
            mode = pair.first;
        }
    }
    
    // Print the mode of the all deque elements
    cout << "Mode of All Elements in Deque is: " << mode << endl;

    return 0;
}

Output

Mode of All Elements in Deque is: 4

Time Complexity: O(N), where N is the size of the deque.
Auxiliary Space: O(N)