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bsearch

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< c‎ | algorithm

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C
 
Algoritmi
qsort
bsearch
 
Elemento definito nell'header <stdlib.h>
void* bsearch( const void* key, const void* ptr, size_t count, size_t size,
               int (*comp)(const void*, const void*) );
Trova un elemento pari a elemento puntato da key in un array puntato da ptr. La matrice contiene elementi count di size dimensioni. Funzione puntato da comp viene utilizzato per confronto oggetto.
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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Indice

[modifica] Parametri

key -
puntatore all'elemento da ricercare
Original:
pointer to the element to search for
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ptr -
puntatore alla matrice da esaminare
Original:
pointer to the array to examine
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count -
numero di elemento della matrice
Original:
number of element in the array
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size -
dimensione di ciascun elemento della matrice in byte
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.

​

[modifica] Valore di ritorno

puntatore all'elemento trovato o NULL altrimenti.
Original:
pointer to the found element or NULL otherwise.
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[modifica] Esempio

#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

[modifica] Vedi anche
Ordina un intervallo di elementi di tipo non specificato
Original:
sorts a range of elements with unspecified type
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(funzione) [modifica]
C++ documentation for bsearch
Estratto da "https://it.cppreference.com/mwiki/index.php?title=c/algorithm/bsearch&oldid=24543"