The list doesn’t have random access operator [] to access elements by indices, because std::list internally store elements in a doubly-linked list. So, to access an element at any Kth location, the idea is to iterate one by one from beginning to Kth element. Instead of iterating for K times. For this, an STL std::advance() function is used to find it in linear time.
Syntax:
advance(InputIterator& it, Distance N)
Parameters: This function accepts two parameters i.e., iterator that is to be traversed through the list and the position to where it has to be moved. The position can be negative for random access and bidirectional iterators.
Return Type: This function has no return type.
Below is the C++ implementation of the above approach:
C++
// C++ program to access Kth element // of the list using advanced #include <bits/stdc++.h> using namespace std; // Driver Code int main() { // Create list with initial value 100 list<int> li(5, 100); // Insert 20 and 30 to the list li.push_back(20); li.push_back(30); // Elements of list are // 100, 100, 100, 100, 100, 20, 30 // Initialize iterator to list list<int>::iterator it = li.begin(); // Move the iterator by 5 elements advance(it, 5); // Print the element at the it cout << *it; return 0; } |
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