Most viewed questions in C++

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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 do I set up Visual Studio Code to compile C++ code?

Although the Visual Studio Code editor from ...READ MORE

Aug 17, 2022 in C++ by Nicholas
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1,062 views
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What is the difference between std::list<std::pair> and std::map in C++ STL?

What distinguishes std::list<std::pair> from std::map? Does the ...READ MORE

Aug 17, 2022 in C++ by Nicholas
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How can i sort a map by its .second parameter

How can I output all the int ...READ MORE

Jul 28, 2022 in C++ by Nicholas
• 7,760 points
1,057 views
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Insert object at index of vector c++

I have to add a new item to the existing object vector.  Although I am aware that an iterator must be used, I am not entirely sure how it operates. I need to insert a new item by name in the precise index that I found after some searching into an alphabetically sorted vector.  I have this, then. vector<Person>people; int index =54; Person temp; people.push_back(temp);//insert at end of ...READ MORE

Aug 5, 2022 in C++ by Nicholas
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Difference between 'struct' and 'typedef struct' in C++?

In C++, is there any difference between: struct Foo ...READ MORE

Aug 8, 2022 in C++ by Nicholas
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Using "super" in C++

The following phrase is part of my coding approach: class Derived : public Base { ...READ MORE

Jul 13, 2022 in C++ by Nicholas
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What is the difference between cout, cerr, clog of iostream header in c++? When to use which one?

I looked up the differences between cout, ...READ MORE

Jul 27, 2022 in C++ by Nicholas
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What really is a deque in STL?

A deque is defined somewhat recursively: fundamentally, ...READ MORE

Jun 10, 2022 in C++ by Damon
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1,043 views
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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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Check if element found in array c++

How can I see if the element ...READ MORE

Nov 17, 2022 in C++ by Ashwini
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1,034 views
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Socket Programming in C++

The C++ Standard does not have a ...READ MORE

Aug 2, 2022 in C++ by Damon
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1,029 views
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Differentiate between function overloading and function overriding

Differentiate between function overloading and function overriding ...READ MORE

Aug 17, 2022 in C++ by Nicholas
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1,028 views
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Successor of INT_MAX and INT_MIN

I have two inquiries. Is 1e9 smaller than ...READ MORE

Jul 15, 2022 in C++ by Nicholas
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1,028 views
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How to find if a given key exists in a C++ std::map

I'm trying to check if a given ...READ MORE

Jul 14, 2022 in C++ by Nicholas
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1,024 views
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Code Not working in VS Code but works in OnlineGDB

I am practicing about primeSieve with C++ language in VS Code 1.57.1. Can ...READ MORE

Jun 1, 2022 in C++ by Nicholas
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1,016 views
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Why should I use reference variables at all?

References themselves are unrelated to the issue. The issue is because C++ manages object lifetimes differently from run-time systems that employ garbage collectors, such as Java.  There is no standard built-in garbage collector in C++.  Both automatic (within local or global scope) and manual (explicitly allocated/deallocated in heap) object lifetimes are possible in  C++. A C++ reference is nothing more than an object's alias.  It has no knowledge of object lifespan (for the sake of efficiency).  The coder must give it some thought.  A reference bound to a temporary object is an exception; in this situation, the temporary object's lifespan is prolonged to include the lifetime of the bound reference. References play a crucial role in the fundamental ideas of C++, and they are required for 90% of jobs.  Otherwise, pointers must be used, which is typically far worse. You can use references, for instance, when you need to give an object as a function parameter by reference rather than by value: void f(A copyOfObj); ...READ MORE

Aug 5, 2022 in C++ by Damon
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Storing C++ template function definitions in a .CPP file

I have some template code that I'd rather have saved in a CPP file rather than inline in the header.  I know this is possible if you know which template types will be utilised.  As an example: .h file class foo { public: template <typename ...READ MORE

Jul 26, 2022 in C++ by Nicholas
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996 views
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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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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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991 views
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Adding to a vector of pair

I have a pair vector that looks like this: vector<pair<string,double>> revenue; I'd want to add a string and a double from a map that looks like this: revenue[i].first = "string"; revenue[i].second = map[i].second; However, because revenue is not initialised, it returns an out of bounds error.  So I ...READ MORE

Jul 26, 2022 in C++ by Nicholas
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988 views
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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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Cases of static and dynamic binding in C++

When an object's static type is used to associate it with a member function, this is known as static binding (understand the type of its class). When a pointer or reference is associated with a member function based on the dynamic type of the object, this is known as dynamic binding (understand the instance of the variable at runtime). Before continuing, keep in mind that dynamic binding only works with pointers, references, and virtual functions for the base class. Because everything needed to call the function is known at compile time, the first call is a static binding (also known as early binding). Derived1 d1(1, 10); d1.display_data(); You already know that the d1 instance is a Derived1 automatic variable, and that it will call the Derived1::display data method (). The first condition is incorrect: d1 is neither a pointer nor a reference. The second condition isn't acceptable:  There is no virtual Derived1::display data. The second call is for ...READ MORE

Jun 7, 2022 in C++ by Damon
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How can I convert a std::string to int?

There are some new convert methods in C++ that convert std::string to a numeric type. As an alternative to str.c str() atoi(str.c str()) atoi(str.c str() you can make use of std::stoi std::stoi ...READ MORE

Jun 1, 2022 in C++ by Damon
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973 views
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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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967 views
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C++ auto keyword. Why is it magic?

Auto was a keyword that C++ "inherited" from C and had been around for a long time but was almost never used because there were only two possibilities: it wasn't allowed or it was assumed by default. C++11 introduced the usage of auto to denote an inferred type. Similarly to how template type deduction works for function templates, auto x = initializer deduces the type of x from the type of initializer.  Consider the following function template: template<class T> int whatever(T t) { ...READ MORE

Jun 21, 2022 in C++ by Damon
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962 views
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Run C++ in command prompt - Windows

What may be the cause? I know ...READ MORE

Jul 22, 2022 in C++ by Nicholas
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959 views
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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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943 views
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memory allocation for objects

In C++, a variable like int x ...READ MORE

Aug 16, 2022 in C++ by Nicholas
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935 views
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Accumulate function in Vector (STL) giving negative sum

I'm receiving a negative total when I run the code below (-294967296). #include<iostream> #include<vector> #include<numeric> using namespace std; int main() { ...READ MORE

Jul 22, 2022 in C++ by Nicholas
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935 views
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Function default argument value depending on argument name in C++ [duplicate]

When the function is called with no argument for the corresponding parameter, the default argument is evaluated.  In a default argument, a parameter must not appear as a potentially evaluated expression.  A function's parameters declared before a default argument are in scope and can obscure the namespace and class member name. It provides the following example: int h(int a, ...READ MORE

Jun 7, 2022 in C++ by Damon
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935 views
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how the iterator in c++ could be printed?

Suppose, I have declared a vector in C++ like ...READ MORE

Jul 11, 2022 in C++ by Nicholas
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932 views
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const int *p vs. int const *p - Is const after the type acceptable?

My coworker is 0 for 2 on questions inspired by him (1, 2), so I decided to give him a chance to catch up. Our most recent argument is about the placement of "const" on declarations. He believes it should be placed either in front of the type or after the pointer.  The explanation is that this is what everyone else does, and different styles are likely to be confusing.  Thus, a constant pointer to int and a constant pointer to int would be: const int *i; ...READ MORE

Jul 22, 2022 in C++ by Nicholas
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927 views
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What is the fastest way to transpose a matrix in C++?

I have a reasonably large matrix that I need to transpose.  Assume, for example, that my matrix is a b c d e f g h ...READ MORE

Jul 15, 2022 in C++ by Nicholas
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920 views
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How can I get the size of a C++ function?

In C++, how can I find the size& ...READ MORE

Aug 5, 2022 in C++ by Nicholas
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919 views
0 votes
1 answer

Reverse Contents in Array

My strategy would be as follows: #include <algorithm> #include <iterator> int main() { const int ...READ MORE

Aug 5, 2022 in C++ by Damon
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917 views
0 votes
1 answer

Syntax of priority queue

We must first include the queue header file in order to establish a priority queue in C++. #include <queue> Once we import this file, we ...READ MORE

May 31, 2022 in C++ by Damon
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912 views
0 votes
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functions in c++ call by value and call by reference

Calling a function by value copies the argument and stores it in a local variable for use by the function, so the argument is unaffected if the value of the local variable changes.  The argument is passed to the function as a reference rather than a copy, so if the function changes the value of the argument, the argument is also changed.   The void change(int); function prototype informs the compiler that there is a function named change that takes a single int argument and returns void (i.e. nothing).  Because there is no & with the argument, it is called by value.  You have the line change(orig); later in your code, which actually calls the function with. Take a look at the output of ...READ MORE

Jun 7, 2022 in C++ by Damon
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911 views
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Static vs dynamic type checking in C++

I'm curious in the differences between static ...READ MORE

Jul 1, 2022 in C++ by Nicholas
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904 views
0 votes
1 answer

When to use virtual destructors?

When you want to delete an instance of a derived class using a pointer to the base class, virtual destructors come in handy: class Base { // ...READ MORE

Jun 7, 2022 in C++ by Damon
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904 views
0 votes
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How do you properly use namespaces in C++?

I come from a Java background where ...READ MORE

Aug 8, 2022 in C++ by Nicholas
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902 views
0 votes
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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898 views
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Simple dictionary in C++

Changing some Python code to C++. BASEPAIRS = { "T": "A", "A": "T", ...READ MORE

Jul 26, 2022 in C++ by Nicholas
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896 views
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Nested try...catch inside C++ exception handler?

I may wish to run code that might throw an exception in my exception handler. Is the following C++ structure acceptable?  Are there any drawbacks if so? try { // ... } catch (const ...READ MORE

Aug 5, 2022 in C++ by Nicholas
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880 views
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What are Containers/Adapters? C++

What exactly are containers/adapters? I am familiar ...READ MORE

Aug 8, 2022 in C++ by Nicholas
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879 views
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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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877 views
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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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877 views
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In C, are arrays pointers or used as pointers?

First, look at this code When this is ...READ MORE

Aug 11, 2022 in C++ by krishna
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875 views
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C++ vector erase function not working properly

Here is the code I want to use to delete any entries with values more than 2 and fewer than 5. vector<int> myvector{3, 3, 3, 3, 3, 3, ...READ MORE

Jul 11, 2022 in C++ by Nicholas
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873 views
0 votes
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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867 views