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Acciones

std::find, std::find_if, std::find_if_not

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< cpp‎ | algorithm
 
 
Algoritmo biblioteca
Funciones
Original:
Functions
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Para no modificar la secuencia de las operaciones
Original:
Non-modifying sequence operations
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find
find_if
find_if_not


(C++11)
find_end
find_first_of
adjacent_find
search
search_n
Modificación de la secuencia de operaciones
Original:
Modifying sequence operations
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Particionamiento operaciones
Original:
Partitioning operations
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Clasificación de las operaciones (en rangos ordenados)
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Sorting operations (on sorted ranges)
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Las operaciones binarias de búsqueda (en rangos ordenados)
Original:
Binary search operations (on sorted ranges)
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Conjunto de operaciones (en rangos ordenados)
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Set operations (on sorted ranges)
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Operaciones del montón
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Heap operations
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Mínimo / máximo de operaciones
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Minimum/maximum operations
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Operaciones numéricas
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Numeric operations
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C biblioteca
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C library
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Defined in header <algorithm>
template< class InputIt, class T >
InputIt find( InputIt first, InputIt last, const T& value );
(1)
template< class InputIt, class UnaryPredicate >

InputIt find_if( InputIt first, InputIt last,

                 UnaryPredicate p );
(2)
template< class InputIt, class UnaryPredicate >

InputIt find_if_not( InputIt first, InputIt last,

                     UnaryPredicate q );
(3) (desde C++11)

Estas funciones buscan el primer elemento del rango [first, last) que satisface ciertos criterios:

1. find Busca un elemento igual a value

2. find_if Busca un elemento para el cual el predicado p devuelve true

3. find_if_not busca un elemento para el cual el predicado q devuelve false

Contenido

[editar] Parámetros

first, last - el rango de elementos a examinar
value - valor a buscar
p - unary predicate which returns ​true para el elemento requerido.

The signature of the predicate function should be equivalent to the following:

 bool pred(const Type &a);

The signature does not need to have const &, but the function must not modify the objects passed to it.
The type Type must be such that an object of type InputIt can be dereferenced and then implicitly converted to Type. ​

q - unary predicate which returns ​false para el elemento requerido.

The signature of the predicate function should be equivalent to the following:

 bool pred(const Type &a);

The signature does not need to have const &, but the function must not modify the objects passed to it.
The type Type must be such that an object of type InputIt can be dereferenced and then implicitly converted to Type. ​

Type requirements
-
InputIt must meet the requirements of InputIterator.

[editar] Valor de retorno

Iterador al primer elemento que satisface la condición o last si no se encuentra dicho elemento.

[editar] Complejidad

A lo sumo last - first aplicaciones del predicado.

[editar] Posible implementación

First version
template<class InputIt, class T>
InputIt find(InputIt first, InputIt last, const T& value)
{
    for (; first != last; ++first) {
        if (*first == value) {
            return first;
        }
    }
    return last;
}
Second version
template<class InputIt, class UnaryPredicate>
InputIt find_if(InputIt first, InputIt last, UnaryPredicate p)
{
    for (; first != last; ++first) {
        if (p(*first)) {
            return first;
        }
    }
    return last;
}
Third version
template<class InputIt, class UnaryPredicate>
InputIt find_if_not(InputIt first, InputIt last, UnaryPredicate q)
{
    for (; first != last; ++first) {
        if (!q(*first)) {
            return first;
        }
    }
    return last;
}
Si usted no tiene C + +11, un equivalente a std::find_if_not es utilizar std::find_if con el predicado negado .
Original:
If you do not have C++11, an equivalent to std::find_if_not is to use std::find_if with the negated predicate.
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template<class InputIt, class UnaryPredicate>
InputIt find_if_not(InputIt first, InputIt last, UnaryPredicate q)
{
    return std::find_if(first, last, std::not1(q));
}

[editar] Ejemplo

El siguiente ejemplo busca un entero en un vector de enteros.

#include <iostream>
#include <algorithm>
#include <vector>
 
int main()
{
    int n1 = 3;
    int n2 = 5;
 
    std::vector<int> v{0, 1, 2, 3, 4};
 
    auto result1 = std::find(v.begin(), v.end(), n1);
    auto result2 = std::find(v.begin(), v.end(), n2);
 
    if (result1 != v.end()) {
        std::cout << "v contains: " << n1 << '\n';
    } else {
        std::cout << "v does not contain: " << n1 << '\n';
    }
 
    if (result2 != v.end()) {
        std::cout << "v contains: " << n2 << '\n';
    } else {
        std::cout << "v does not contain: " << n2 << '\n';
    }
}

Output:

v contains: 3
v does not contain: 5

[editar] Ver también

encuentra dos idénticas (o alguna otra relación) elementos adyacentes el uno al otro
Original:
finds two identical (or some other relationship) items adjacent to each other
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(función de plantilla) [edit]
encuentra la última secuencia de elementos en un cierto rango
Original:
finds the last sequence of elements in a certain range
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(función de plantilla) [edit]
searches for any one of a set of elements
(función de plantilla) [edit]
encuentra la primera posición donde dos rangos diferentes
Original:
finds the first position where two ranges differ
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(función de plantilla) [edit]
searches for a range of elements
(función de plantilla) [edit]