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bsearch

Da cppreference.com
< c‎ | algorithm

Defined in header <stdlib.h>
void* bsearch( const void* key, const void* ptr, size_t count, size_t size,
               int (*comp)(const void*, const void*) );
Localiza um elemento igual ao elemento apontado por key em uma matriz apontada por ptr. A matriz contém elementos count de size tamanho. Função apontada pelo comp é usado para comparação de objetos.
Original:
Finds an element equal to element pointed to by key in an array pointed to by ptr. The array contains count elements of size size. Function pointed to by comp is used for object comparison.
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Índice

[editar] Parâmetros

key -
ponteiro para o elemento para pesquisar
Original:
pointer to the element to search for
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ptr -
ponteiro para a matriz para examinar
Original:
pointer to the array to examine
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count -
número de elementos na matriz
Original:
number of element in the array
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size -
tamanho de cada elemento na matriz em bytes
Original:
size of each element in the array in bytes
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comp - comparison function which returns ​a negative integer value if the first argument is less than the second,

a positive integer value if the first argument is greater than the second and zero if the arguments are equal. key is passed as the first argument, an element from the array as the second.
The signature of the comparison function should be equivalent to the following:

 int cmp(const void *a, const void *b);

The function must not modify the objects passed to it.

[editar] Valor de retorno

ponteiro para o elemento encontrado ou de outro modo.. NULL
Original:
pointer to the found element or NULL otherwise.
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[editar] Exemplo

#include <stdlib.h>
#include <stdio.h>
 
struct data {
  int nr;
  char const *value;
} dat[] = {
  {1, "Foo"}, {2, "Bar"}, {3, "Hello"}, {4, "World"}
};
 
int data_cmp(void const *lhs, void const *rhs) {
  struct data const *const l = lhs;
  struct data const *const r = rhs;
  return l->nr < r->nr;
}
 
int main(void) {
  struct data key = { .nr = 3 };
  struct data const *res = bsearch(&key, dat, sizeof(dat)/sizeof(dat[0]),
                                   sizeof(dat[0]), data_cmp);
  if(!res) {
    printf("No %d not found\n", key.nr);
  }
  else {
    printf("No %d: %s\n", res->nr, res->value);
  }
}

Output:

No 3: Hello

[editar] Veja também

Classifica um intervalo de elementos de tipo não especificado
Original:
sorts a range of elements with unspecified type
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(função) [edit]
C++ documentation for bsearch