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

unordered_set::load_factor()是C++ STL中的內置函數，該函數返回unordered_set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_set_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_set::load_factor()函數：

示例1:：

// C++ program to illustrate the 
// unordered_set::load_factor() function 
#include <iostream> 
#include <unordered_set> 
using namespace std; 
  
int main() 
{ 
  
    // declaration 
    unordered_set<int> sample; 
  
    // inserts element 
    sample.insert(1); 
    sample.insert(11); 
    sample.insert(111); 
    sample.insert(12); 
    sample.insert(13); 
  
    cout << "The size is: " << sample.size(); 
    cout << "\nThe bucket_count is: "
         << sample.bucket_count(); 
  
    cout << "\nThe load_factor is: "
         << sample.load_factor(); 
  
    sample.insert(2); 
    sample.insert(22); 
  
    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(33); 
  
    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

示例2:：

// C++ program to illustrate the 
// unordered_set::load_factor() function 
#include <iostream> 
#include <unordered_set> 
using namespace std; 
  
int main() 
{ 
  
    // declaration 
    unordered_set<char> sample; 
  
    // inserts element 
    sample.insert('a'); 
    sample.insert('b'); 
    sample.insert('c'); 
    sample.insert('r'); 
    sample.insert('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('f'); 
    sample.insert('k'); 
  
    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'); 
  
    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

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注：本文由純淨天空篩選整理自Aman Goyal 2大神的英文原創作品 unordered_set 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。