unordered_multimap::load_factor()是C++ STL中的内置函数,该函数返回unordered_multimap容器中的当前负载系数。负载系数是容器中的元素数量(其大小)与铲斗数量(bucket_count)之比:
load_factor = size / bucket_count
负载因子会影响哈希表中发生冲突的概率(即,两个元素位于同一存储桶中的概率)。通过在每次需要扩展时进行重新哈希处理,容器会自动增加铲斗数,以将负载系数保持在特定阈值以下(其max_load_factor)。
用法:
unordered_multimap_name.load_factor()
参数:该函数不接受任何参数。
返回值:该函数返回当前的负载系数。它可以是整数或双精度类型。
以下示例程序旨在说明unordered_multimap::load_factor()函数:
程序1:
// C++ program to illustrate the
// unordered_multimap::load_factor() function
#include <iostream>
#include <unordered_map>
using namespace std;
int main()
{
// declaration
unordered_multimap<int, int> sample;
// inserts element
sample.insert({ 1, 2 });
sample.insert({ 1, 3 });
sample.insert({ 2, 4 });
sample.insert({ 5, 8 });
sample.insert({ 7, 10 });
cout << "The size is: " << sample.size();
cout << "\nThe bucket_count is: "
<< sample.bucket_count();
cout << "\nThe load_factor is: "
<< sample.load_factor();
sample.insert({ 1, 1 });
sample.insert({ 9, 0 });
cout << "\n\nThe size is: "
<< sample.size();
cout << "\nThe bucket_count is: "
<< sample.bucket_count();
cout << "\nThe load_factor is: "
<< sample.load_factor();
sample.insert({ 1, 1 });
cout << "\n\nThe size is: "
<< sample.size();
cout << "\nThe bucket_count is: "
<< sample.bucket_count();
cout << "\nThe load_factor is: "
<< sample.load_factor();
return 0;
}
输出:
The size is: 5 The bucket_count is: 7 The load_factor is: 0.714286 The size is: 7 The bucket_count is: 17 The load_factor is: 0.411765 The size is: 8 The bucket_count is: 17 The load_factor is: 0.470588
程序2:
// C++ program to illustrate the
// unordered_multimap::load_factor()
#include <iostream>
#include <unordered_map>
using namespace std;
int main()
{
// declaration
unordered_multimap<char, char> sample;
// inserts element
sample.insert({ 'a', 'b' });
sample.insert({ 'a', 'b' });
sample.insert({ 'a', 'd' });
sample.insert({ 'b', 'e' });
sample.insert({ 'b', 'd' });
cout << "The size is: " << sample.size();
cout << "\nThe bucket_count is: "
<< sample.bucket_count();
cout << "\nThe load_factor is: "
<< sample.load_factor();
sample.insert({ 'b', 'k' });
sample.insert({ 'b', 'h' });
cout << "\n\nThe size is: " << sample.size();
cout << "\nThe bucket_count is: "
<< sample.bucket_count();
cout << "\nThe load_factor is: "
<< sample.load_factor();
sample.insert({ 'z', 'j' });
cout << "\n\nThe size is: " << sample.size();
cout << "\nThe bucket_count is: "
<< sample.bucket_count();
cout << "\nThe load_factor is: "
<< sample.load_factor();
return 0;
}
输出:
The size is: 5 The bucket_count is: 7 The load_factor is: 0.714286 The size is: 7 The bucket_count is: 17 The load_factor is: 0.411765 The size is: 8 The bucket_count is: 17 The load_factor is: 0.470588
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注:本文由纯净天空筛选整理自gopaldave大神的英文原创作品 unordered_multimap load_factor() function in C++ STL。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。