std::
unordered_map::bucket_size
公众成员函数 <unordered_map>size_type bucket_size ( size_type n ) const;
返回存储桶的容量
返回存储桶 n中的元素个数。
桶是容器内部哈希表中的一个槽，元素根据哈希值被分配给它。
bucket中元素的数量会影响访问bucket中特定元素所需的时间。容器会自动增加桶的数量， 以保持负载系数(即桶的平均大小)低于max_load_factor。
☲ 参数
- n
-
桶编号.
这个值应该小于bucket_count。
size_type是一种无符号整型.
☉ 返回值
桶 n中的元素个数.
size_type是一种无符号整型。
☣ 示例
// unordered_map::bucket_size
#include <iostream>
#include <string>
#include <unordered_map>
int main ()
{
std::unordered_map<std::string,std::string> mymap = {
{"us","United States"},
{"uk","United Kingdom"},
{"fr","France"},
{"de","Germany"}
};
unsigned nbuckets = mymap.bucket_count();
std::cout << "mymap has " << nbuckets << " buckets:\n";
for (unsigned i=0; i<nbuckets; ++i) {
std::cout << "bucket #" << i << " has " << mymap.bucket_size(i) << " elements.\n";
}
return 0;
} |
输出:
mymap has 5 buckets:
bucket #0 has 0 elements.
bucket #1 has 1 elements.
bucket #2 has 2 elements.
bucket #3 has 0 elements.
bucket #4 has 1 elements.
mymap has 5 buckets:
bucket #0 has 0 elements.
bucket #1 has 1 elements.
bucket #2 has 2 elements.
bucket #3 has 0 elements.
bucket #4 has 1 elements.
✥ 复杂度
桶size线性。
☣ 迭代器的有效性
不变
🍄 另请参阅
| unordered_map::bucket_count | 返回存储桶的数量(公众成员函数) |
| unordered_map::bucket | 定位元素的存储桶(公众成员函数) |
| unordered_map::size | 返回容量(公众成员函数) |