Difference between revisions of "cpp/container/vector/capacity"
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Latest revision as of 20:32, 3 July 2017
| size_type capacity() const; |
(noexcept since C++11) (constexpr since C++20) |
|
Returns the number of elements that the container has currently allocated space for.
Contents |
[edit] Parameters
(none)
[edit] Return value
Capacity of the currently allocated storage.
[edit] Complexity
Constant.
[edit] Example
Run this code
#include <iomanip> #include <iostream> #include <vector> int main() { int sz = 100; std::vector<int> v; auto cap = v.capacity(); std::cout << "Initial size: " << v.size() << ", capacity: " << cap << '\n'; std::cout << "\nDemonstrate the capacity's growth policy." "\nSize: Capacity: Ratio:\n" << std::left; while (sz-- > 0) { v.push_back(sz); if (cap != v.capacity()) { std::cout << std::setw( 7) << v.size() << std::setw(11) << v.capacity() << std::setw(10) << v.capacity() / static_cast<float>(cap) << '\n'; cap = v.capacity(); } } std::cout << "\nFinal size: " << v.size() << ", capacity: " << v.capacity() << '\n'; }
Possible output:
Initial size: 0, capacity: 0 Demonstrate the capacity's growth policy. Size: Capacity: Ratio: 1 1 inf 2 2 2 3 4 2 5 8 2 9 16 2 17 32 2 33 64 2 65 128 2 Final size: 100, capacity: 128
[edit] See also
| returns the number of elements (public member function) | |
| reserves storage (public member function) |
