Latest questions in C++

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How to use the priority queue STL for objects?

class Person { public: int age; }; I'd want to put objects of the type Person in a priority queue. priority_queue< ...READ MORE

Jun 27, 2022 in C++ by Nicholas
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Can you use "cin" with string?

To enter a string, I was instructed to use gets(str) rather than cin.  In the programme below, though, I can use cin perfectly well.  Could you please tell me if you can use cin?  Please accept my apologies for my poor English.  The application allows you to enter up to five names and then print them on the screen. The code is as follows: #include <iostream> #include <string.h> using namespace std; int main() { ...READ MORE

Jun 27, 2022 in C++ by Nicholas
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C++ pointer to objects

Is it always necessary in C++ to  ...READ MORE

Jun 27, 2022 in C++ by Nicholas
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692 views
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How can I get the maximum or minimum value in a vector?

In C++, how can I find the greatest or minimum value in a vector? Is it correct to assume that it would be similar with an array? Do I require an iterator?  I tried max element, but I kept receiving errors. vector<int>::const_iterator it; it = max_element(cloud.begin(), cloud.end()); error: request for ...READ MORE

Jun 27, 2022 in C++ by Nicholas
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What is the easiest way to initialize a std::vector with hardcoded elements?

I can make an array and initialise&nb ...READ MORE

Jun 27, 2022 in C++ by Nicholas
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779 views
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Binary literals?

Binary literals will be supported in  ...READ MORE

Jun 27, 2022 in C++ by Damon
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c++ constructor and copy constructor

In a pre-C++17 compiler, this is known as copy elision (test it with C++17 on compiler explorer or wandbox with -std=c++17 vs. -std=c++14 flags).  As of C++17, the compiler must delete numerous instances of copy and move constructors and create objects directly without the need of intermediary objects. Unlike A a { 10 }; the line A a ...READ MORE

Jun 27, 2022 in C++ by Damon
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In C++ abs( *a - *b) does not return absolute value of negative number

On the first line, you reallocated *a, and it is now utilising that new value on the second line.  int origa = *a; *a = abs(origa + ...READ MORE

Jun 27, 2022 in C++ by Damon
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1 answer

How can I get all the unique keys in a multimap

This method worked for me. for( multimap<char,int>::iterator it ...READ MORE

Jun 27, 2022 in C++ by Damon
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1,862 views
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1 answer

Using :: (scope resolution operator) in C++

You're mostly correct regarding cout and cin. ...READ MORE

Jun 27, 2022 in C++ by Damon
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820 views
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1 answer

How does #include <bits/stdc++.h> work in C++? [duplicate]

#include <bits/stdc++.h> is a precompiled header implementation ...READ MORE

Jun 21, 2022 in C++ by Damon
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9,332 views
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Difference between function overloading and method overloading

They are interchangeable. Some people, on the other hand, prefer calling methods, functions that are part of a class, and functions, free functions. //function overloading void foo(int x); void foo(int x, int ...READ MORE

Jun 21, 2022 in C++ by Damon
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5,608 views
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When to use extern in C++

This is useful when dealing with global variables.  Global variables are declared in a header so that any source file that contains the header is aware of them, but you only need to "define" them once in one of your source files. To explain, using extern int x; informs the compiler that an int object named x exists elsewhere.  It is not the compiler's responsibility to know where it exists; it just needs to know the type and name so that it may utilise it.  After compiling all of the source files, the linker will resolve all x references to the one definition found in one of the generated source files. For it to operate, the x variable's declaration must have "external linkage," which simply means that it must be defined outside of a function (at what's known as "the file scope") and without the static keyword. header: #ifndef HEADER_H #define HEADER_H // any source file that ...READ MORE

Jun 21, 2022 in C++ by Damon
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What range of values can integer types store in C++

You may rely on the following minimal ...READ MORE

Jun 21, 2022 in C++ by Damon
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1,202 views
0 votes
1 answer

insert method for doubly linked list C++

I attempted to repair all of your methods, and I believe I succeeded; at least, the current test example prints the proper answer: #include <iostream> #include <vector> using namespace std; struct Node { ...READ MORE

Jun 21, 2022 in C++ by Damon
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1,200 views
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how could I use the power function in c/c++ without pow(), functions, or recursion

It is part of a series.  Replace pow() with the previous iteration's value. There is no need for code to call pow ().  Pow(x, 5 * I - 1) and pow(-1, I - 1) may be formed since both have an int exponent dependent on the iterator I from the previous loop iteration. Example: Let f(x, i) = pow(x, 5 * i ...READ MORE

Jun 21, 2022 in C++ by Damon
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2,979 views
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1 answer

What is a Class and Object in C++?

A Class is like a blueprint, an ...READ MORE

Jun 21, 2022 in C++ by Damon
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795 views
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1 answer

Difference between Turbo C++ and Borland C++ compiler [closed]

I will try my best to respond, ...READ MORE

Jun 21, 2022 in C++ by Damon
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Explanation of function pointers

It's a little perplexing. Function type and pointer to function type are distinct kinds (no more similar than int and pointer to int).  However, in virtually all cases, a function type decays to a reference to a function type.  In this context, rotting roughly refers to conversion (there is a difference between type conversion and decaying, but you are probably not interested in it right now). What matters is that practically every time you use a function type, you end up with a reference to the function type.  But take note of the nearly - almost every time is not always! And there are rare circumstances where it does not. typedef void(functionPtr)(int); functionPtr fun = function; This code tries to clone one function to another (not the pointer! the function!)  However, this is not feasible since functions in C++ cannot be copied.  The compiler does not let this, and I'm surprised you got it compiled (you say you got linker errors?) Now for the code: typedef void(functionPtr)(int); functionPtr function; function(5); function does ...READ MORE

Jun 21, 2022 in C++ by Damon
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1 answer

C++ code file extension? What is the difference between .cc and .cpp [closed]

GNU GCC recognizes all of the following ...READ MORE

Jun 21, 2022 in C++ by Damon
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2,043 views
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1 answer

How to convert string to char array in C++?

Simplest way I can think of doing ...READ MORE

Jun 20, 2022 in C++ by Damon
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6,325 views
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1 answer

How to use enums in C++

This will be sufficient to declare your ...READ MORE

Jun 20, 2022 in C++ by Damon
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933 views
0 votes
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Difference between 'new operator' and 'operator new'?

What is difference between "new operator" and ...READ MORE

Jun 15, 2022 in C++ by Nicholas
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557 views
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1 answer

Use of "this" keyword in C++ [duplicate]

Yes, it is optional and generally omitted.  However, it may be essential for accessing variables after they have been overridden in the scope: Person::Person() { int age; ...READ MORE

Jun 20, 2022 in C++ by Damon
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725 views
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1 answer

What is the name of the "<<" and ">>" operators? [duplicate]

This operator (<<) applied to an output ...READ MORE

Jun 20, 2022 in C++ by Damon
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670 views
0 votes
1 answer

What is compile-time polymorphism and why does it only apply to functions?

"Compile time polymorphism" used to signify function overloading.  It only applies to functions because that's all you can overload. Templates in modern C++ modify this.  One example has previously been provided by Neil Butterworth.  Another technique is template specialisation.  As an example: #include <iostream> #include <string> template <class T> struct my_template { ...READ MORE

Jun 20, 2022 in C++ by Damon
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1 answer

How to use new[ ] and delete[ ] operator in C++

int main(){ char *str; ...READ MORE

Jun 20, 2022 in C++ by Damon
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856 views
0 votes
1 answer

abstract class and virtual functions

Is this class considered abstract because it only contains one virtual function?  I could still build an Animal object and use getFoodCost(); No. In C++, a "Abstract Class" is often a class having a single pure virtual function: class Abstract { public: virtual ...READ MORE

Jun 20, 2022 in C++ by Damon
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1,034 views
0 votes
1 answer

C++ override inherited methods

Child::init is now concealing Father::init and not overriding it.  In order to receive dynamic dispatch, your init member function must be virtual: virtual void init () { ...READ MORE

Jun 20, 2022 in C++ by Damon
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854 views
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1 answer

Vector of Vectors to create matrix

Before accessing any elements, you must first set the vector of vectors to the right size.  You may do it this way: // assumes using std::vector for brevity vector<vector<int>> matrix(RR, ...READ MORE

Jun 16, 2022 in C++ by Damon
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1,754 views
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1 answer

How do i apply lower_bound to a range of unsorted vector elements?

What's the point of sorting your array? ...READ MORE

Jun 15, 2022 in C++ by Damon
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2,263 views
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1 answer

Where are the Microsoft Visual C++ 2015-2022 Redistributable (x64) packages installed?

They are, in my opinion, at their best. C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Redist\MSVC It's worth noting ...READ MORE

Jun 15, 2022 in C++ by Damon
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9,550 views
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1 answer

C++ string in classes

The std namespace contains the string class. You need change the class to something like this: class Language { public: ...READ MORE

Jun 15, 2022 in C++ by Damon
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1,541 views
0 votes
1 answer

Easiest way to convert int to string in C++

std::stoi (and variations for each numeric type) ...READ MORE

Jun 15, 2022 in C++ by Damon
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1,414 views
0 votes
1 answer

What is a lambda expression in C++11?

In C++11, what is a lambda expression? A: It's the object of an autogenerated class with overloading operator() const under the hood.  Closure is a type of object that is produced by the compiler.  This 'closure' idea is similar to C++11's bind notion.  Lambdas, on the other hand, usually produce better code.  Full inlining is also possible with calls through closures. Q: When do you think I'd utilise one? A: Define "simple and tiny logic" and request that the compiler generate the code from the preceding question.  You tell the compiler the expressions you wish to be inside the operator ().  The compiler will produce everything else for you. Q: What kind of problem do they tackle that couldn't be solved before they were introduced? A: It's some form of syntactic sugar, like using operators instead of functions for custom add, subtract, and other operations... However, wrapping 1-3 lines of genuine logic to some classes, and so on, saves additional lines of needless code!  Some engineers believe that if the number of lines is reduced, there is a lower likelihood of mistakes (which I agree with). Example of usage auto x = [=](int arg1){printf("%i", ...READ MORE

Jun 15, 2022 in C++ by Damon
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1 answer

Mac M1 C++20: Missing std::convertible_to and std::forward_iterator concepts

Clang from Homebrew is a good option (or compile one by yourself).  You may also look at the features that have been incorporated on Clang's official website. ❯ clang++ --version Homebrew clang version 13.0.0 Target: arm64-apple-darwin21.1.0 Thread ...READ MORE

Jun 14, 2022 in C++ by Damon
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775 views
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1 answer

Has Windows an integrated built-in C/C++ compiler package?

Microsoft does not offer a compiler or ...READ MORE

Jun 14, 2022 in C++ by Damon
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1,995 views
0 votes
1 answer

Error "Microsoft Visual C++ 14.0 is required (Unable to find vcvarsall.bat)"

For pip, use the binary-only option.  ...READ MORE

Jun 14, 2022 in C++ by Damon
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1,302 views
0 votes
1 answer

Lower and Upper Bound in case of Decreasing/Non-ascending vector

Both std::lower bound and std::upper bound must have an increasing (non-decreasing) order as their objective. By giving a comparator as the 4th parameter of the functions, you may modify the meaning of "growing." To work with descending vectors, use std::greater. #include<iostream> #include<vector> #include<algorithm> #include<functional> using namespace std; int main() { ...READ MORE

Jun 14, 2022 in C++ by Damon
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1,753 views
0 votes
1 answer

The Definitive C++ Book Guide and List

Introductory, no previous programming experience Book Author(s) Description review C++ Primer* * Not ...READ MORE

Jun 14, 2022 in C++ by Damon
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983 views
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1 answer

What exactly does stringstream do?

When converting between strings and other numerical kinds, stringstream can be very useful.  Stringstream is comparable to iostream in terms of usage, so learning it is not difficult. Stringstreams can be used to read strings as well as write data into them.  It mostly works with a string buffer instead of an actual I/O channel. The stringstream class's fundamental member functions are as follows: str() is a function that returns the contents of a buffer as a string. str(string), which changes the buffer's contents to the string argument. Here's an example of how string streams can be used. ostringstream os; os << "dec: " << 15 ...READ MORE

Jun 13, 2022 in C++ by Damon
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1 answer

Ceil function: how can we implement it ourselves?

You can disassemble the components of an IEEE754 floating point number and put the logic together yourself: #include <cstring> float my_ceil(float f) { ...READ MORE

Jun 13, 2022 in C++ by Damon
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edited Jun 14, 2022 by Hemant 1,618 views
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casting int to char using C++ style casting [duplicate]

Even though the precision is lost, yo ...READ MORE

Jun 13, 2022 in C++ by Damon
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21,384 views
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1 answer

outputting ascii table in C++

This line doesn't do the right thing: ch ...READ MORE

Jun 13, 2022 in C++ by Damon
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1,432 views
0 votes
1 answer

str_lib_facilities.h file from Stroustrup's Programming: Principles and Practice Using C++ generating errors

Switching the compiler to compile in c++11 ...READ MORE

Jun 13, 2022 in C++ by Damon
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1,349 views
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1 answer

std::next_permutation Implementation Explanation

Permutations are generated in lexicographical order by ...READ MORE

Jun 10, 2022 in C++ by Damon
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968 views
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1 answer

How do I erase an element from std::vector<> by index?

You might perform the following to remove a single element: std::vector<int> vec; vec.push_back(6); vec.push_back(-17); vec.push_back(12); // Deletes the second element (vec[1]) vec.erase(std::next(vec.begin())); Alternatively, to remove many elements at once: // ...READ MORE

Jun 10, 2022 in C++ by Damon
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1,926 views
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What is the difference between std::__gcd and std::gcd?

I done some research about this. The ...READ MORE

Jun 10, 2022 in C++ by Damon
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2,220 views
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1 answer

C++ - Decimal to binary converting

The.to string() function of std::bitset returns a std::string containing a binary text representation with leading-zero padding. Use std::bitset32> to get 32-character strings from 32-bit integers, or std::bitset32> to get 32-character strings from 32-bit integers. #include <iostream> #include <bitset> int main() { ...READ MORE

Jun 10, 2022 in C++ by Damon
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832 views
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1 answer

Why we actually need runtime polymorphism?

One of the most significant elements of ...READ MORE

Jun 10, 2022 in C++ by Damon
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1,580 views