Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://cplusplus.com/unordered_set::rehash below:

public member function

<unordered_set>

void rehash ( size_type n );

Set number of buckets

If n is greater than the current number of buckets in the container (bucket_count), a rehash is forced. The new bucket count can either be equal or greater than n.

If n is lower than the current number of buckets in the container (bucket_count), the function may have no effect on the bucket count and may not force a rehash.

A rehash is the reconstruction of the hash table: All the elements in the container are rearranged according to their hash value into the new set of buckets. This may alter the order of iteration of elements within the container.

Rehashes are automatically performed by the container whenever its load factor is going to surpass its max_load_factor in an operation.

Notice that this function expects the number of buckets as argument. A similar function exists, unordered_set::reserve, that expects the number of elements in the container as argument.

n

The minimum number of buckets for the container hash table.
Member type size_type is an unsigned integral type.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

// unordered_set::rehash
#include <iostream>
#include <string>
#include <unordered_set>

int main ()
{
  std::unordered_set<std::string> myset;

  myset.rehash(12);

  myset.insert("office");
  myset.insert("house");
  myset.insert("gym");
  myset.insert("parking");
  myset.insert("highway");

  std::cout << "current bucket_count: " << myset.bucket_count() << std::endl;

  return 0;
}

By calling rehash to reserve a certain minimum amount of buckets in the hash table, we avoid the multiple rehashes that the expansion of the container may cause.

unordered_set::reserve

Request a capacity change (public member function)

unordered_set::bucket_count

Return number of buckets (public member function)

unordered_set::max_load_factor

Get or set maximum load factor (public member function)

unordered_set::size

Return container size (public member function)

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4