list::clear() in C++ STL

Lists are containers used in C++ to store data in a non contiguous fashion, Normally, Arrays and Vectors are contiguous in nature, therefore the insertion and deletion operations are costlier as compared to the insertion and deletion option in Lists.

clear() function is used to remove all the elements of the list container, thus making it size 0.

Syntax :

listname.clear()
Parameters :
No parameters are passed.
Result :
All the elements of the list are
removed ( or destroyed )

Examples:

Input  : list{1, 2, 3, 4, 5};
         list.clear();
Output : list{}
Input  : list{};
         list.clear();
Output : list{}

Errors and Exceptions

1. It has a no exception throw guarantee.

2. Shows error when a parameter is passed. 

// CPP program to illustrate 
// Implementation of clear() function 
#include <iostream> 
#include <list> 
using namespace std; 

int main() 
{ 
 list<int> mylist{ 1, 2, 3, 4, 5 }; 

 mylist.clear(); 
 // List becomes empty 

 // Printing the list 
 for (auto it = mylist.begin(); it != mylist.end(); ++it) 
  cout << ' ' << *it; 
 return 0; 
} 

Output:

No Output

Time Complexity: O(n)
Auxiliary Space: O(1)

Related Article : Delete elements in C++ STL List