From cppreference.com
voidresize(size_typecount); (1)voidresize(size_typecount,constvalue_type&value); (2)Resizes the container to contain count elements, does nothing if count==size().
If the current size is greater than count, the container is reduced to its first count elements.
If the current size is less than count, then:
2) Additional copies of value are appended.
Parameters
count - new size of the container value - the value to initialize the new elements with Type requirements -T must meet the requirements of
in order to use overload (1). -T must meet the requirements of
in order to use overload (2). Complexity
Linear in the difference between the current size and count.
Notes
If value-initialization in overload (
) is undesirable, for example, if the elements are of non-class type and zeroing out is not needed, it can be avoided by providing a
.
Example
Run this code
#include<list>#include<iostream>voidprint(autorem,conststd::list<int>&c){for(std::cout<<rem;constintel:c)std::cout<<el<<' ';std::cout<<'\n';}intmain(){std::list<int>c={1,2,3};print("The list holds: ",c);c.resize(5);print("After resize up to 5: ",c);c.resize(2);print("After resize down to 2: ",c);c.resize(6,4);print("After resize up to 6 (initializer = 4): ",c);}Output:
The list holds: 1 2 3 After resize up to 5: 1 2 3 0 0 After resize down to 2: 1 2 After resize up to 6 (initializer = 4): 1 2 4 4 4 4 Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior
C++98 random-access iterators were used to determine the erase range use bidirectional iterators
C++98 resize() passed value by value passes by const reference
C++98 the behavior of resize(size()) was not specified specified See also
returns the maximum possible number of elements
(public member function)
returns the number of elements
(public member function)
checks whether the container is empty
(public member function)