std::
unordered_set::bucket_count
公众成员函数 <unordered_set>size_type bucket_count() const noexcept;
返回存储桶的数量
返回unordered_set容器中的桶数。
桶是容器内部哈希表中的一个槽，元素根据其哈希值被分配。
桶的数量直接影响容器哈希表的负载系数 load factor (从而影响碰撞的概率)。容器会自动增加桶的数量， 以保持负载系数低于特定的阈值(它的max_load_factor)，每次需要增加桶的数量时都会导致rehash。
☲ 参数
- none
☉ 返回值
当前桶的数量.
size_type是一种无符号整型。
☣ 示例
// unordered_set::bucket_count
#include <iostream>
#include <string>
#include <unordered_set>
int main ()
{
std::unordered_set<std::string> myset =
{"Mercury","Venus","Earth","Mars","Jupiter","Saturn","Uranus","Neptune"};
unsigned n = myset.bucket_count();
std::cout << "myset has " << n << " buckets.\n";
for (unsigned i=0; i<n; ++i) {
std::cout << "bucket #" << i << " contains:";
for (auto it = myset.begin(i); it!=myset.end(i); ++it)
std::cout << " " << *it;
std::cout << "\n";
}
return 0;
} |
输出:
myset has 11 buckets.
bucket #0 contains:
bucket #1 contains: Venus
bucket #2 contains: Jupiter
bucket #3 contains:
bucket #4 contains: Neptune Mercury
bucket #5 contains:
bucket #6 contains: Earth
bucket #7 contains: Uranus Saturn
bucket #8 contains: Mars
bucket #9 contains:
bucket #10 contains:
myset has 11 buckets.
bucket #0 contains:
bucket #1 contains: Venus
bucket #2 contains: Jupiter
bucket #3 contains:
bucket #4 contains: Neptune Mercury
bucket #5 contains:
bucket #6 contains: Earth
bucket #7 contains: Uranus Saturn
bucket #8 contains: Mars
bucket #9 contains:
bucket #10 contains:
✥ 复杂度
常量
☣ 迭代器的有效性
不变
🍄 另请参阅
| unordered_set::bucket | 定位元素的存储桶(公众成员函数) |
| unordered_set::bucket_size | 返回存储桶的大小(公众成员函数) |
| unordered_set::load_factor | 返回存储桶的元素平均数量（负载系数）(公众成员函数) |
| unordered_set::max_load_factor | 获取或设置存储桶最大的负载系数(公众成员函数) |