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Page 1469 of 2109
What uses are there for "placement new" in C++?
In this section we will see what is the placement new operator in C++. This placement new is another variation of new operator. The normal new operator performs two things. It allocates memory, and then constructs an object in allocated memory.The new operator allocates memory in the heap section and constructs objects there. But for the placement new operator, it constructs object at the given address. To deallocate memory, we can use delete keyword if the memory is allocated using new operator. But for placement new there is no placement delete feature.So in a nutshell, placement new allows you to ...
Read MoreCalling virtual functions inside constructors in C++
Virtual functions calling from a constructor or destructor is dangerous and should be avoided whenever possible as the virtual function we call is called from the Base class and not from the derived class.The reason is that in C++ Super-classes are constructed before derived classes. So, in the following example, as B must be instantiated, before D is instantiated. When B's constructor is called, it's not D yet, so the virtual function table still has the entry for B's copy of s().Example Code#include using namespace std; class B { public: B() { s(); } virtual void s() { cout
Read MoreC++ Program to Implement Traveling Salesman Problem using Nearest Neighbour Algorithm
Here is a C++ Program to Implement Traveling Salesman Problem using Nearest Neighbour Algorithm.Required functions and pseudocodesAlgorithmBegin Initialize c = 0, cost = 1000; Initialize g[][]. function swap() is used to swap two values x and y. function cal_sum() to calculate the cost which take array a[] and size of array as input. Initialize sum = 0. for i = 0 to n compute s+= g[a[i %3]][a[(i+ 1) %3]]; if (cost >s) cost = s function permute() is used to perform permutation: if ...
Read MoreC++ Program to Apply Above-Below-on Test to Find the Position of a Point with respect to a Line
This is a C++ program to apply Above-Below-on Test to find the position of a point with respect to a Line. For any point t (xt, yt) on the plane, its position with respect to the line L connecting m and n is found by calculating the scalar s −Y = A xt + B yt + CIf Y< 0, t lies in the clockwise halfplane of L; if Y>0, t lies on the counter-clockwise halfplane; if Y= 0, t lies on L.AlgorithmBegin Take the points as input. For generating equation of the line, generate random numbers for ...
Read MoreC++ Program to Implement the RSA Algorithm
RSA is an asymmetric cryptography algorithm which works on two keys-public key and private key.AlgorithmsBegin 1. Choose two prime numbers p and q. 2. Compute n = p*q. 3. Calculate phi = (p-1) * (q-1). 4. Choose an integer e such that 1 < e < phi(n) and gcd(e, phi(n)) = 1; i.e., e and phi(n) are coprime. 5. Calculate d as d ≡ e−1 (mod phi(n)); here, d is the modular multiplicative inverse of e modulo phi(n). 6. For encryption, c = me mod n, where m = original message. 7. For ...
Read MoreHow to stop C++ console application from exiting immediately?
Sometimes we have noticed that the console is being closed immediately after displaying the result. So we cannot see the result properly. Here we will see how we can stop the console from closing.The idea is very simple. We can use the getchar() function at the end. This will wait for one character. If one character is pressed, the console will exit.Example#include using namespace std; int main() { cout
Read Moreisnormal() in C++
In this section we will see the isnormal() function in C++. This function is present in the cmath library. This function is used to check whether a number is normal or not. The numbers that are considered as non-normal are zeros, infinity or NAN.This function takes float, double or long double values as argument. Returns 1 if the number is normal, otherwise returns 0.Example#include #include using namespace std; int main() { cout
Read MoreWhen should we write our own assignment operator in C++?
Here we will see when we need to create own assignment operator in C++. If a class do not have any pointers, then we do not need to create assignment operator and copy constructor. C++ compiler creates copy constructor and assignment operator for each class. If the operators are not sufficient, then we have to create our own assignment operator.Example#include using namespace std; class MyClass { //no user defined assignment operator or copy constructor is present int *ptr; public: MyClass (int x = 0) { ptr = new int(x); } void setValue (int x) { *ptr = x; } void print() { cout
Read MoreShuffle vs random_shuffle in C++
Here we will see the Shuffle and random_shuffle in C++. Let us see the random_shuffle first. It is used to randomly rearrange the elements in range [left, right). This function randomly swaps the positions of each element with the position of some randomly chosen positions.We can provide some random generator function to tell which element will be taken in every case. If we do not provide some, it will use its own random generator function.Example#include using namespace std; int myRandomGenerator(int j) { return rand() % j; } main() { srand(unsigned(time(0))); vector arr; for (int j ...
Read MoreBind function and placeholders in C++
Here we will see the Bind function and the placeholders in C++. Sometimes we need to manipulate the operation of some functions as we need. We can use some default parameters to get some essence of manipulating.In C++11, one new feature is introduced, called the bind function. This helps us to do such manipulating in some easier fashion. To use these features, we have to use header file.Bind functions with the help of placeholders helps to determine the positions, and number of arguments to modify the function according to desired outputs.Placeholders are namespaces which detect the position of a ...
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