How to Find Frequency of an Element in a List in C++? (original) (raw)

Last Updated : 10 Apr, 2024

In C++, lists are sequence containers that allow non-contiguous memory allocation. They are implemented as doubly-linked lists. The frequency of a specific element means how many times that particular element occurs in a list. In this article, we will learn how to find the frequency of a specific element in a list in C++ STL.

**Example:

**Input:
myList = {10, 31, 20, 31, 31, 40};
Target = 31

**Output:
Frequency of 31 is : 3

Find the Frequency of an Element in a List in C++

To find the frequency of a specific element in a std::list in C++, we can use the std::count() method that counts the occurrences of a given target value within a specified range in a list.

Syntax to Find Frequency of an Element in C++

****count(**listName.begin(), listName.end(), target);

Here,

• **begin() and **end() are input iterators to the initial and final positions of the sequence of elements.
• **target is the element whose frequency is required.

C++ Program to Find the Frequency of a Specific Element in a List

The below example demonstrates how we can use the std::count() function to find the frequency of a specific element in a list in C++ STL.

C++ `

// C++ program to illustrate how to find the frequency of a // specific element in a list

#include #include #include using namespace std;

int main() { // Initializing a list of integers list myList = { 10, 31, 20, 31, 31, 40 };

// Declare element whose frequency is required
int target = 31;

// Finding the frequency of the target element
int frequency
    = count(myList.begin(), myList.end(), target);

// Printing the frequency of the element
cout << "Frequency of " << target
     << " is : " << frequency << endl;

return 0;

}

`

Output

Frequency of 31 is : 3

**Time Complexity: O(N), where N is the number of elements in the list.
**Auxiliary Space: O(1)