Trending questions in C++

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Why use #define instead of a variable

What is the purpose of the #define ...READ MORE

Jul 1, 2022 in C++ by Nicholas
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446 views
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What does the C++ standard state the size of int, long type to be?

I'm seeking for specific information on the sizes of basic C++ types.  I understand that it is determined by the architecture (16 bits, 32 bits, or 64 bits) and the compiler. But are there any C++ standards? On a 32-bit architecture, I'm using Visual Studio 2008.  This is what I get: char : 1 byte short : 2 ...READ MORE

Jul 5, 2022 in C++ by Nicholas
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504 views
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How do I reverse a C++ vector?

The algorithm header has a method std::reverse for this purpose. #include <vector> #include <algorithm> int main() { std::vector<int> ...READ MORE

Jun 27, 2022 in C++ by Damon
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How to use c++ swap function?

It is OK to write swap(a,b); There is an issue when I write swap(&c[0],&d[0]);.  Can anyone explain why? #include<iostream> #include<algorithm> using namespace std; int main(void){ ...READ MORE

Jul 1, 2022 in C++ by Nicholas
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404 views
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C++ Singleton design pattern

I recently came upon a C++ realization/implementation of the Singleton design pattern.  It looked like this (I took it from a real-life example): // a lot of methods are omitted ...READ MORE

Jul 4, 2022 in C++ by Nicholas
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520 views
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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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Reverse a number without converting it to string in C++

I'm attempting to write a programme in C++ to reverse a number. It works well with numbers like 1234, but when I try to enter a number like 5430, it displays 345, and the same with numbers that begin with zero, such as 0234, which displays 432. Could someone please explain how to deal with zeros at the beginning and end of a sentence? I simply need to save the number without converting it to a string. #include<iostream> using namespace std; int main(){ ...READ MORE

Jun 30, 2022 in C++ by Nicholas
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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 1,407 views
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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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1,054 views
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Deep copy vs Shallow Copy

What's the distinction between deep and shallow ...READ MORE

Jun 29, 2022 in C++ by Nicholas
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646 views
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What does "#include <iostream>" do?

You must include it in order to read or write to the standard input/output streams. int main( int argc, char * argv[] ...READ MORE

Jun 28, 2022 in C++ by Damon
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683 views
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Selection sort in C++ (modified) not working for all cases

I was attempting to tweak the selection sort code in C++ in order to test the results.  My updated code is as follows: #include<bits/stdc++.h> using namespace std; int main() { ...READ MORE

Jun 29, 2022 in C++ by Damon
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603 views
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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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1,228 views
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1 answer

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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952 views
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1 answer

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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800 views
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1 answer

Is 'If Else' statement indentation important or not in C++? [duplicate]

White space has no effect on the understanding of code in C and C++.  That is not to say that the programmer should be unconcerned about its misuse. The easiest method to demonstrate what the above code truly represents is to specify all of the inferred braces directly, as seen below.  The 'if then' or 'otherwise' clause only affects one line of code in the if statement with no brackets. This is one of the reasons why people strive to insist on 'proper coding standards' to guarantee that other people can clearly grasp the programmer's flow and meaning. while(c != cols) { ...READ MORE

Jun 27, 2022 in C++ by Damon
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668 views
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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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1,422 views
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Difference between set.upper_bound() and upper_bound(set.begin(), set.end()) stl

I discovered that set.upper bound() was quicker ...READ MORE

Jun 29, 2022 in C++ by Damon
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538 views
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Is the std::set iteration order always ascending according to the C++ specification?

According to what I've read, std::set in ...READ MORE

Jun 29, 2022 in C++ by Nicholas
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526 views
0 votes
1 answer

The static keyword and its various uses in C++

Static variables exist during the "lifetime" of the translation unit in which they are declared, and: It cannot be accessible from any other translation unit if it is in a namespace scope (i.e. outside of functions and classes).  This is referred to as "internal linking" or "static storage lifetime."  (Except for constexpr, do not do this in headers; otherwise, you would wind up with a different variable in each translation unit, which is really confusing.) If it is a variable in a function, it, like any other local variable, cannot be accessed from outside the function.  (This is the mentioned local) Class members have no limited scope owing to static, but they may be referenced from both the class and an instance (like std::string::npos). locations as code: static std::string namespaceScope = "Hello"; void ...READ MORE

Jun 27, 2022 in C++ by Damon
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643 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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680 views
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What is the STL?

I'm not a C++ coder, thus I ...READ MORE

Jun 29, 2022 in C++ by Damon
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514 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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1,236 views
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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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670 views
0 votes
1 answer

What does the explicit keyword mean?

To resolve the parameters to a function, the compiler is permitted to do one implicit conversion.  This implies that the compiler can utilise constructors with a single argument to convert from one type to another to find the correct type for a parameter. Here's an example class with a constructor ...READ MORE

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

Initializing a two dimensional std::vector

Assume you wish to start a 2D vector, m*n, with a value of 0. We could do it. #include<iostream> int main(){ int ...READ MORE

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

lower_bound == upper_bound

Lower bound: the initial greater-or-equal element. Upper bound: ...READ MORE

Jun 21, 2022 in C++ by Damon
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1,174 views
0 votes
1 answer

Use of multisets in C++ [duplicate]

Because a multi-set does not need the storage of single-element objects.  You're considering storing anything in a multi-set, such as a string.  But it is not its intended use.  You may use whatever struct you want and compare it to a single element in the struct. As an example: struct PhoneBookEntry { std::string name; ...READ MORE

Jun 27, 2022 in C++ by Damon
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581 views
0 votes
1 answer

Binary literals?

Binary literals will be supported in  ...READ MORE

Jun 27, 2022 in C++ by Damon
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684 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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1,117 views
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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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553 views
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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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552 views
0 votes
0 answers

Sorting Characters Of A C++ String

Is there a built-in method for sorting characters in a string, or do I have to construct my own? for instance: string word = "dabc"; I would want to ...READ MORE

Jun 27, 2022 in C++ by Nicholas
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548 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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658 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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1,140 views
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1 answer

How to pass in command line arguments when using ideone?

It appears that you won't be able ...READ MORE

Jun 21, 2022 in C++ by Damon
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1,108 views
0 votes
1 answer

Easiest way to convert int to string in C++

C++ adds std::stoi (and variants for each numeric type) and std::to string, which are the C equivalents of atoi and itoa but expressed in terms of std::string #include <string> std::string s = std::to_string(42); Is therefore ...READ MORE

Jun 1, 2022 in C++ by Damon
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1,665 views
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Why are exceptions so rarely used in C++

I've been writing in C++ on and ...READ MORE

Jun 29, 2022 in C++ by Damon
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390 views
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1 answer

C++ multiset, return key at position?

A set (or multiset) is typically represented ...READ MORE

Jun 27, 2022 in C++ by Damon
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504 views
0 votes
1 answer

How does virtual inheritance solve the "diamond" (multiple inheritance) ambiguity?

You desire: (Achievable with virtual inheritance) ...READ MORE

Jun 10, 2022 in C++ by Damon
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1,252 views
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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
• 7,760 points
459 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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856 views
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1 answer

C++ - Overloading vs Overriding in Inheritance

In C++, a derived class's method only overrides the base class's method if their declarations match (I say "match," but I'm not sure what the formal term is).  That is, all arguments must be of the same type, with the same const qualification.  If there are any mismatches, the derived class's method hides all methods with the same name rather than overriding.  This is what the "ERROR" in your image is attempting to convey.  So, in that image, / overrides in a comment is incorrect and misleading. Yes, many C++ instructors are unaware of these somewhat esoteric details. Furthermore, if you want to override, your base class's method must be virtual; otherwise, polymorphism will not work.  We could also say that the derived-class method hides the base-class method if it wasn't virtual.  The part about hiding, on the other hand, has almost no meaning here; what this term really means is that you're not in charge. Furthermore, overloading is the presence of multiple methods with the same name but different signatures, as you may have noticed. To be useful, they must all be present in the derived class; otherwise, they will be hidden if the derived class only has one method, fa1, and the other fa1 are in the base.  There is, however, a syntax sugar that "copies" all fa1 from the base to the derived. class A { public: void fa1(); ...READ MORE

Jun 7, 2022 in C++ by Damon
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1,299 views
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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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808 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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754 views
0 votes
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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615 views
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1 answer

What is the best way to use a HashMap in C++?

The ordered and unordered map containers (std::map and std::unordered map) are included in the standard library.  The items in an ordered map are sorted by key, and insert and access are in O (log n).  For ordered maps, the standard library often use red black trees.  However, this is only an implementation detail.  Insert and access are in O in an unordered map (1).  It is simply another term for a hashtable. An illustration using (ordered) std::map: #include <map> #include <iostream> #include <cassert> int main(int argc, char ...READ MORE

Jun 10, 2022 in C++ by Damon
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1,076 views
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1 answer

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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598 views
0 votes
1 answer

implementing merge sort in C++

To respond to the question:  std::vectorT> is used to create dynamically sized arrays at runtime.  Ideally, you'd use one of these to get feedback.  If not, they are simple to convert.  For instance, you might make two arrays like this: template <typename T> void merge_sort(std::vector<T>& array) { ...READ MORE

Jun 10, 2022 in C++ by Damon
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1,072 views
0 votes
1 answer

std::greater on a an std::pair of a double and a class

std::greater is simply a wrapper for a ...READ MORE

Jun 2, 2022 in C++ by Damon
• 4,960 points
1,375 views