pbds in c++
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;
ordered_set ord_set;
int a;
ord_set.insert(a);
*ord_set.find_by_order(a);
ord_set.order_of_key(a);new c++
MyClass * p1 = new MyClass;
// allocates memory by calling: operator new (sizeof(MyClass))
// and then constructs an object at the newly allocated space
MyClass * p2 = new (std::nothrow) MyClass;
// allocates memory by calling: operator new (sizeof(MyClass),std::nothrow)
// and then constructs an object at the newly allocated space
new (p2) MyClass;
// does not allocate memory -- calls: operator new (sizeof(MyClass),p2)
// but constructs an object at p2
// Notice though that calling this function directly does not construct an
//object:
MyClass * p3 = (MyClass*) ::operator new (sizeof(MyClass));
// allocates memory by calling: operator new (sizeof(MyClass))
// but does not call MyClass's constructor
delete p1;
delete p2;
delete p3;new in c++
//placement new in c++
char *buf = new char[sizeof(string)]; // pre-allocated buffer
string *p = new (buf) string("hi"); // placement new
string *q = new string("hi"); // ordinary heap allocation
/*Standard C++ also supports placement new operator, which constructs
an object on a pre-allocated buffer. This is useful when building a
memory pool, a garbage collector or simply when performance and exception
safety are paramount (there's no danger of allocation failure since the memory
has already been allocated, and constructing an object on a pre-allocated
buffer takes less time):
*/new in c++
#include <iostream>
#include <string>
using String = std::string;
class Entity
{
private:
String m_Name;
public:
Entity() : m_Name("Unknown") {}
Entity(const String& name) : m_Name(name) {}
const String& GetName() const {
return m_Name;
};
};
int main() {
// new keyword is used to allocate memory on heap
int* b = new int; // new keyword will call the c function malloc which will allocate on heap memory = data and return a ptr to that plaock of memory
int* c = new int[50];
Entity* e1 = new Entity;//new keyword Not allocating only memory but also calling the constructor
Entity* e = new Entity[50];
//usually calling new will call underlined c function malloc
//malloc(50);
Entity* alloc = (Entity*)malloc(sizeof(Entity));//will not call constructor only allocate memory = memory of entity
delete e;//calls a c function free
Entity* e3 = new(c) Entity();//Placement NewCopyright © 2021 Codeinu
Forgot your account's password or having trouble logging into your Account? Don't worry, we'll help you to get back your account. Enter your email address and we'll send you a recovery link to reset your password. If you are experiencing problems resetting your password contact us
