std::unordered_set::begin, std::unordered_set::cbegin - cppreference.com

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`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().

Parametri

(nessuno)

Valore restituito

Iteratore al primo elemento

Complessità

Costante Template:cpp/container/constant iterator note

Example

#include <iostream>
#include <unordered_set>

struct Point { double x, y; };

int main() {
    Point pts[3] = { {1, 0}, {2, 0}, {3, 0} };
    
    //points is a set containing the addresses of points
    std::unordered_set<Point *> points = { pts, pts + 1, pts + 2 };
    
    //Change each y-coordinate of (i, 0) from 0 into i^2 and print the point
    for(auto iter = points.begin(); iter != points.end(); ++iter){
        (*iter)->y = ((*iter)->x) * ((*iter)->x); //iter is a pointer-to-Point*
        std::cout << "(" << (*iter)->x << ", " << (*iter)->y << ") ";
    }
    std::cout << '\n';
    
    //Now using the range-based for loop, we increase each y-coordinate by 10
    for(Point * i : points) {
        i->y += 10;
        std::cout << "(" << i->x << ", " << i->y << ") ";
    }
}

Possible output:

(3, 9) (1, 1) (2, 4) 
(3, 19) (1, 11) (2, 14)

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) [modifica]