Namespace
Varianti

std::unordered_map::begin, std::unordered_map::cbegin

Da cppreference.com.
 
 
 
std::unordered_map
Membri funzioni
Original:
Member functions
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unordered_map::unordered_map
unordered_map::~unordered_map
unordered_map::operator=
unordered_map::get_allocator
Iteratori
Original:
Iterators
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unordered_map::begin
unordered_map::cbegin
unordered_map::end
unordered_map::cend
Capacità
Original:
Capacity
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unordered_map::erase
unordered_map::size
unordered_map::max_size
Modificatori
Original:
Modifiers
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unordered_map::clear
unordered_map::insert
unordered_map::emplace
unordered_map::emplace_hint
unordered_map::erase
unordered_map::swap
Lookup
Original:
Lookup
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unordered_map::count
unordered_map::find
unordered_map::equal_range
Benna interfaccia
Original:
Bucket interface
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unordered_map::begin2
unordered_map::end2
unordered_map::bucket_count
unordered_map::max_bucket_count
unordered_map::bucket_size
unordered_map::bucket
Politica di Hash
Original:
Hash policy
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unordered_map::load_factor
unordered_map::max_load_factor
unordered_map::rehash
unordered_map::reserve
Osservatori
Original:
Observers
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
unordered_map::hash_function
unordered_map::key_eq
 
iterator begin() noexcept;
const_iterator begin() const noexcept;
const_iterator cbegin() const noexcept;

Restituisce un iteratore al primo elemento del container.

Se il container è vuoto, l'iteratore restituito sarà uguale a end().

range-begin-end.svg

Indice

[modifica] Parametri

(nessuno)

[modifica] Valore restituito

Iteratore al primo elemento

[modifica] Complessità

Costante


[modifica] Example

#include <cmath>
#include <iostream>
#include <unordered_map>
 
struct Node { double x, y; };
 
int main() {
    Node nodes[3] = { {1, 0}, {2, 0}, {3, 0} };
 
    //mag is a map mapping the address of a Node to its magnitude in the plane
    std::unordered_map<Node *, double> mag = {
        { nodes,     1 },
        { nodes + 1, 2 },
        { nodes + 2, 3 }
    };
 
    //Change each y-coordinate from 0 to the magnitude
    for(auto iter = mag.begin(); iter != mag.end(); ++iter){
        auto cur = iter->first; // pointer to Node
        cur->y = mag[cur]; // could also have used  cur->y = iter->second;
    }
 
    //Update and print the magnitude of each node
    for(auto iter = mag.begin(); iter != mag.end(); ++iter){
        auto cur = iter->first;
        mag[cur] = std::hypot(cur->x, cur->y);
        std::cout << "The magnitude of (" << cur->x << ", " << cur->y << ") is ";
        std::cout << iter->second << '\n';
    }
 
    //Repeat the above with the range-based for loop
    for(auto i : mag) {
        auto cur = i.first;
        cur->y = i.second;
        mag[cur] = std::hypot(cur->x, cur->y);
        std::cout << "The magnitude of (" << cur->x << ", " << cur->y << ") is ";
        std::cout << mag[cur] << '\n';
        //Note that in contrast to std::cout << iter->second << '\n'; above, 
        // std::cout << i.second << '\n'; will NOT print the updated magnitude
    }
}

Possible output:

The magnitude of (3, 3) is 4.24264
The magnitude of (1, 1) is 1.41421
The magnitude of (2, 2) is 2.82843
The magnitude of (3, 4.24264) is 5.19615
The magnitude of (1, 1.41421) is 1.73205
The magnitude of (2, 2.82843) is 3.4641

[modifica] Vedi anche

restituisce un iteratore fino alla fine
Original:
returns an iterator to the end
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(metodo pubblico) [edit]