A std::pair is an ordered, heterogeneous sequence of exactly two objects (it is a special case of std::tuple).
std::pair is a part of the C++ Standard Library, defined in the header <utility>.
Questions tagged [std-pair]
776 questions
17
votes
1 answer
std::pair return type
I was playing around with auto in std::pair. In the below code, function f is supposed to return a std::pair of types which depend on a template parameter.
A working example:
EXAMPLE 1
template
auto f()
{
if constexpr (S == 1)
…
mfnx
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17
votes
4 answers
How do I initialize a const std::pair?
Let's say that I've got a :
#include
using namespace std;
typedef pair my_pair;
how do I initialize a const my_pair ?
Maciek
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16
votes
3 answers
Difference between make_pair and curly brackets { } for assigning a pair in C++?
I didn't find anyone answering this, is there any difference between the following :
v.push_back({x, y});
and :
v.push_back(make_pair(x, y));
Assuming that v was declared this way :
vector > v;
Noueman Khalikine
- 309
- 3
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16
votes
5 answers
Sorting a std::vector> by the string?
How can I sort this vector by comparing the pair.first which is an std::string? (without providing a static compare function, nor use boost).
jmasterx
- 52,639
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16
votes
2 answers
Sorting a vector of pairs
I have a question about sorting a vector of pairs:
std::vector> baryProc;
this vector is already filled up with the pairs.
Now I wanted to sort the pairs inside the vector based on the double value inside the…
user2633791
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16
votes
2 answers
lower_bound of vector of pairs with lambda
I want to find the std::lower_bound of the a std::vector of std::pair's according to the second element with lambda.
std::vector < std::pair > vec;
vec.resize(5);
auto it = std::lower_bound(vec.begin(), vec.end(), lambda);
// what is…
Shibli
- 5,879
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15
votes
1 answer
Why do `initializer_list` and `initializer_list` behave differently?
The following code compiles and runs :
#include
#include
#include
#include
void ext( std::initializer_list >> myList )
{
//Do…
Gael Lorieul
- 3,006
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- 50
15
votes
5 answers
Equivalent of C++ STL container "pair" in Objective-C?
I'm new to Objective-C, so please don't judge me too much. I was wondering: Is there an equivalent of the C++ STL pair container I can use in Objective-C?
I want to build an array that contains an NSInteger associated to an NSBool. I know I could…
Michael Eilers Smith
- 8,466
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15
votes
7 answers
Custom sort vector of pair based on their values
I have the following vector:
std::vector< std::pair > vectorOfPairs
with the following items:
0, 1
0, 2
1, 4
2, 3
3, 4
4, 5
5, 6
I would like to sort them in a way that the second component of every pair is equal to the first component…
Alex S. Diaz
- 2,637
- 2
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14
votes
2 answers
How would one push back an empty vector of pairs to another vector?
std::vector > > offset_table;
for (int i = 0; i < (offset.Width()*offset.Width()); ++i)
{
offset_table.push_back( std::vector< std::pair > );
}
This is my code, but I am getting the…
pearbear
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12
votes
3 answers
Different behavior when trying to swap two variables using {} and std::make_pair()
I was trying to swap two variables using std::tie() as per the following code (I am aware of std::swap, I was just trying this out of curiosity):
#include
#include
using std::cin; using std::tie;
using std::cout; using…
Shubham
- 2,847
- 4
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- 37
12
votes
4 answers
Implementation of lower_bound on vector pairs
I know we need to include some compare function in order to achieve this.
But not able to write for this one.
For example:
Elements of vector={(2,4),(4,2),(5,1),(5,3)}
to find=5
lower_bound() should return 2
code->
#define pp pair
bool…
user2826957
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11
votes
1 answer
One liner tuple/pair unpack in c++ with reusing same variable multiple times
I have already seen Is there a one-liner to unpack tuple/pair into references? and know how the unpack values from tuple/pairs in a single line like following
auto [validity, table] = isFieldPresentAndSet(r, "is_federated");
here…
Mayukh Sarkar
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11
votes
3 answers
Forward declaration of objects with STL containers
Consider the following code snippet, where the first line serves only as forward declaration
class A;
followed by defining new class
class B
{
vector Av; //line 1
map Am; //line 2
pair Ap; //line 3
};
line 1 and line 2…
user6386155
- 825
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11
votes
3 answers
Is there a NULL equivalent for pairs in C++?
What would I want to use instead of NULL if I have an unassigned pair in C++?
As an example, suppose I have (pseudo)code like the following:
pair bestPair; //Global variable
updateBestPair(vector a, vector b) {
bestPair =…
user1634426
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