How to Find Last Occurrence of an Element in a List in C++?

Last Updated : 16 Apr, 2024

In C++, std::list represents a doubly linked list and the last occurrence of an element in a list refers to the last time that element appears in the list when traversed from the beginning. In this article, we will learn how to find the last occurrence of a specific element in a list in C++.

Example:

Input:   list<int> myList = {1, 2, 7, 4, 5, 7, 8}  int key = 7;    Output:   The last occurrence of element 7 is found at index :  5

Find the Last Occurrence of an Element in a List in C++

To find the last occurrence of an element in a std::list, we can use the std::find() function with reverse iterators std::list::rbegin() and std::list::rend() to iterate through the list in reverse order. When we iterate in reverse order, the first occurrence is the last occurrence of that element.

Approach

Use the std::find function along with reverse iterators to get the iterator pointing to the first occurrence of the target element from the last.
If the element is found calculate its index using the std::distance function. Pass the base iterator (which points to one position past the end of the list in a forward direction) and the begin iterator to this function.
Since list indexing is zero-based, subtract one from the result obtained from the std::distance function to get the correct index.
Finally, print the index which denotes the last occurrence of the specific element in the list.

C++ Program to Find the Last Occurrence of an Element in a List

The below example demonstrates how to find the last occurrence of a specific element in a given list in C++.

C++

// C++ program to demonstrate how to find the last // occurrence of a specific element in a given list #include <algorithm> #include <iostream> #include <list> using namespace std;  int main() {     // Initializing a list of integers     list<int> myList = { 1, 2, 7, 4, 5, 7, 8 };      // Declare the element whose last occurrence is to be     // found     int element = 7;      // Finding the last occurrence of the element     auto it = find(myList.rbegin(), myList.rend(), element);      // Printing the position of the last occurrence of the     // element     if (it != myList.rend()) {         // Finding the index of the last occurrence of the         // element         int position             = distance(myList.begin(), it.base()) - 1;         cout << "The last occurrence of element " << element              << " is found at index : " << position << endl;     }     else {         cout << "Element not found in the list" << endl;     }     return 0; }

Output

The last occurrence of element 7 is found at index : 5

Time Complexity: O(n), here n is the number of elements in the list.
Auxiliary Space: O(1)

How to Find All Occurrences of an Element in a List in C++?

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How to Find Last Occurrence of an Element in a List in C++?

Find the Last Occurrence of an Element in a List in C++

Approach

C++ Program to Find the Last Occurrence of an Element in a List

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