C++ unordered_multimap load_factor()用法及代碼示例

unordered_multimap::load_factor()是C++ STL中的內置函數，該函數返回unordered_multimap容器中的當前負載係數。負載係數是容器中的元素數量(其大小)與鏟鬥數量(bucket_count)之比：

load_factor = size / bucket_count

負載因子會影響哈希表中發生衝突的概率(即，兩個元素位於同一存儲桶中的概率)。通過在每次需要擴展時進行重新哈希處理，容器會自動增加鏟鬥數，以將負載係數保持在特定閾值以下(其max_load_factor)。

用法：

unordered_multimap_name.load_factor()

參數：該函數不接受任何參數。

返回值：該函數返回當前的負載係數。它可以是整數或雙精度類型。

以下示例程序旨在說明unordered_multimap::load_factor()函數：

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; 
}

輸出：

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; 
}

輸出：

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

相關用法

注：本文由純淨天空篩選整理自gopaldave大神的英文原創作品 unordered_multimap load_factor() function in C++ STL。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。