stdvector Questions
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I'm experimenting with C++20 concepts and I've hit a strange problem I can't explain.
I'm trying to define a concept that checks a given iterator can be incremented (fine), and also checks that the...
Lauer asked 3/8, 2023 at 13:50
7
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What's the fastest way to reset every value of a std::vector<int> to 0 and keeping the vectors initial size ?
A for loop with the [] operator ?
5
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vector<vector<int>> res;
res.emplace_back({1,2}); // change to res.push_back({1,2}); would work
This gives me the error:
main.cpp:61:25: error: no matching function for call to ‘std::v...
1
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Since C++20, std::vector can be used in constant expressions. And as far as I known, current C++ permits dynamically allocate memory under the condition that any such allocation is deallocated by t...
Dele asked 11/6, 2023 at 11:15
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I want to clear a element from a vector using the erase method. But the problem here is that the element is not guaranteed to occur only once in the vector. It may be present multiple times and I n...
29
How do I concatenate two std::vectors?
Miser asked 14/10, 2008 at 15:46
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5
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Could someone tell what is the correct way to work with a vector of arrays?
I declared a vector of arrays (vector<float[4]>) but got error: conversion from 'int' to non-scalar type 'float [...
4
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In order to understand the memory consumption of std::vector<int> I wrote:
std::cout << sizeof(std::vector<int>) << std::endl;
This yields 32. I tried to understand where...
11
When I do this:
std::vector<int> hello;
Everything works great. However, when I make it a vector of references instead:
std::vector<int &> hello;
I get horrible errors like
...
Coterminous asked 28/5, 2009 at 18:4
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I have an array of integers that I need to remove duplicates from while maintaining the order of the first occurrence of each integer. I can see doing it like this, but imagine there is a better wa...
Entangle asked 30/8, 2012 at 15:33
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I had been going through the Book:
C++ Primer, Third Edition By Stanley B. Lippman, Josée Lajoie, found 1 mistake in the program given under the Article 6.3 How a vector Grows Itself, this program ...
2
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Consider the following program:
#include <vector>
#include <iostream>
class A {
int x;
public:
A(int n) noexcept : x(n) { std::cout << "ctor with value\n"; }
A(const...
Bangweulu asked 10/10, 2022 at 8:32
1
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If I have two C++ vectors:
vector<int> a(5) {1,2,3,4,5};
vector<int> b(5) {6,7,8,9,10};
is there a one-line way to use the swap method to swap slices of a and b? Something like
swap(a[...
16
Solved
I have a std::vector<int>, and I want to delete the nth element. How do I do that?
Example:
std::vector<int> vec;
vec.push_back(6);
vec.push_back(-17);
vec.push_back(12);
vec.erase(??...
1
I couldn't understand the syntax of the way the vector root has been initialized with size sz in the constructor - UnionFind(int sz) : root(sz)
class UnionFind {
public:
UnionFind(int sz) :...
Luker asked 1/9, 2022 at 2:55
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So, I have the following:
std::vector< std::vector <int> > fog;
and I am initializing it very naively like:
for(int i=0; i<A_NUMBER; i++)
{
std::vector <int> fogRow;
for(int...
Kipton asked 15/7, 2013 at 20:21
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How much data is copied, when returning a std::vector in a function and how big an optimization will it be to place the std::vector in free-store (on the heap) and return a pointer instead i.e. is:...
Lancewood asked 29/3, 2013 at 13:46
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I know that manual dynamic memory allocation is a bad idea in general, but is it sometimes a better solution than using, say, std::vector?
To give a crude example, if I had to store an array of n ...
Enrollee asked 8/3, 2013 at 12:35
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I have a single even-sized vector that I want to transform into a vector of pairs where each pair contains always two elements. I know that I can do this using simple loops but I was wondering if t...
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I'm reading A Tour of C++ (2nd edition) and I came across this code (6.2 Parameterized Types):
template<typename T>
T* end(Vector<T>& x)
{
return x.size() ? &x[0]+x.size() ...
Mate asked 19/5, 2022 at 10:17
3
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For example, I have such struct in a templated class:
struct Foo{
int data;
vector<Foo*> children;
}
And to print out the data value, I can simply do this: (let bar be a pointer to a Foo...
2
There are several ways to make a vector empty, including
std::vector<int> example = makeMyReallyBigVector();
example.clear();
example.resize(0);
example.erase(example::being(), example::end()...
2
The following question is related, however answers are old, and comment from user Marc Glisse suggests there are new approaches since C++17 to this problem that might not be adequately discussed.
...
Loveinidleness asked 11/2, 2020 at 13:19
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The following code does fail on MSVC but compiles on GCC and Clang, godbolt
#include <unordered_map>
#include <vector>
using namespace std;
struct NonCopyable
{
NonCopyable() = defaul...
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