set::erase

Artículo
06/09/2015

Quita un elemento o un intervalo de elementos de un conjunto de las posiciones especificadas o quita los elementos que coinciden con una clave especificada.

iterator erase(
   const_iterator Where
);
iterator erase(
   const_iterator First,
   const_iterator Last
);
size_type erase(
   const key_type& Key
);

Parámetros

Where
Posición del elemento que se va a quitar.
First
Posición del primer elemento que se va a quitar.
Last
Posición situada más allá del último elemento que se va a quitar.
Key
Valor de clave de los elementos que se van a quitar.

Valor devuelto

Para las dos primeras funciones miembro, iterador bidireccional que designa el primer elemento que permanece más allá de los elementos quitados, o un elemento que es el final del conjunto si no existe ese elemento.

Para la tercera función miembro, devuelve el número de elementos que se han quitado del conjunto.

Ejemplo

// set_erase.cpp
// compile with: /EHsc
#include <set>
#include <string>
#include <iostream>
#include <iterator> // next() and prev() helper functions

using namespace std;

using myset = set<string>;

void printset(const myset& s) {
    for (const auto& iter : s) {
        cout << " [" << iter << "]";
    }
    cout << endl << "size() == " << s.size() << endl << endl;
}

int main()
{
    myset s1;

    // Fill in some data to test with, one at a time
    s1.insert("Bob");
    s1.insert("Robert");
    s1.insert("Bert");
    s1.insert("Rob");
    s1.insert("Bobby");

    cout << "Starting data of set s1 is:" << endl;
    printset(s1);
    // The 1st member function removes an element at a given position
    s1.erase(next(s1.begin()));
    cout << "After the 2nd element is deleted, the set s1 is:" << endl;
    printset(s1);

    // Fill in some data to test with, one at a time, using an intializer list
    myset s2{ "meow", "hiss", "purr", "growl", "yowl" };

    cout << "Starting data of set s2 is:" << endl;
    printset(s2);
    // The 2nd member function removes elements
    // in the range [First, Last)
    s2.erase(next(s2.begin()), prev(s2.end()));
    cout << "After the middle elements are deleted, the set s2 is:" << endl;
    printset(s2);

    myset s3;

    // Fill in some data to test with, one at a time, using emplace
    s3.emplace("C");
    s3.emplace("C#");
    s3.emplace("D");
    s3.emplace("D#");
    s3.emplace("E");
    s3.emplace("E#");
    s3.emplace("F");
    s3.emplace("F#");
    s3.emplace("G");
    s3.emplace("G#");
    s3.emplace("A");
    s3.emplace("A#");
    s3.emplace("B");

    cout << "Starting data of set s3 is:" << endl;
    printset(s3);
    // The 3rd member function removes elements with a given Key
    myset::size_type count = s3.erase("E#");
    // The 3rd member function also returns the number of elements removed
    cout << "The number of elements removed from s3 is: " << count << "." << endl;
    cout << "After the element with a key of \"E#\" is deleted, the set s3 is:" << endl;
    printset(s3);
}

Resultados

Starting data of set s1 is:
 [Bert] [Bob] [Bobby] [Rob] [Robert]
size() == 5

After the 2nd element is deleted, the set s1 is:
 [Bert] [Bobby] [Rob] [Robert]
size() == 4

Starting data of set s2 is:
 [growl] [hiss] [meow] [purr] [yowl]
size() == 5

After the middle elements are deleted, the set s2 is:
 [growl] [yowl]
size() == 2

Starting data of set s3 is:
 [A] [A#] [B] [C] [C#] [D] [D#] [E] [E#] [F] [F#] [G] [G#]
size() == 13

The number of elements removed from s3 is: 1.
After the element with a key of "E#" is deleted, the set s3 is:
 [A] [A#] [B] [C] [C#] [D] [D#] [E] [F] [F#] [G] [G#]
size() == 12