C++ unordered_set::bucket_size() 函式

C++ 的 unordered_set::bucket_size() 函式用於返回第 n 個桶中存在的元素數量。桶是 unordered_set 容器內部雜湊表中的一個槽，元素根據雜湊值分配到該槽中。桶的編號範圍從 0 到 (bucket_count - 1)。

語法

以下是 std::unordered_set::bucket_size() 函式的語法。

size_type bucket_size ( size_type n ) const;

引數

• n − 它表示桶的編號，必須小於 bucket_count。

返回值

此函式返回桶中元素的數量。

示例 1

讓我們看下面的例子，我們將演示 unordered_set::bucket_size() 函式的使用。

#include <iostream>
#include <string>
#include <unordered_set>

int main () {
   std::unordered_set<std::string> myUset = { "sai", "ram", "krishna", "prasad", "tutorials", "point" };
   unsigned nbuckets = myUset.bucket_count();

   std::cout << "myset has " << nbuckets << " buckets:\n";
   for (unsigned i = 0; i < nbuckets; ++i) {
      std::cout << "bucket #" << i << " has " << myUset.bucket_size(i) << " elements.\n";
   }
   return 0;
}

輸出

如果我們執行上面的程式碼，它將生成以下輸出：

myset has 13 buckets:
bucket #0 has 0 elements.
bucket #1 has 0 elements.
bucket #2 has 0 elements.
bucket #3 has 1 elements.
bucket #4 has 0 elements.
bucket #5 has 1 elements.
bucket #6 has 0 elements.
bucket #7 has 0 elements.
bucket #8 has 1 elements.
bucket #9 has 2 elements.
bucket #10 has 0 elements.
bucket #11 has 1 elements.
bucket #12 has 0 elements.

示例 2

考慮下面的例子，我們將查詢指定桶包含的元素數量。

#include <iostream>
#include <string>
#include <unordered_set>
using namespace std;

int main () {
   unordered_set<string> myUset = { "sai", "ram", "krishna", "prasad", "tutorials", "point" };
   unsigned nbuckets = myUset.bucket_count();

   cout << "myUset has " << nbuckets << " buckets:\n";
   cout<<"bucket 5 contains: "<<myUset.bucket_size(5);
   return 0;
}

輸出

以下是上面程式碼的輸出：

myUset has 13 buckets:
bucket 5 contains: 1

示例 3

在下面的示例中，我們將考慮字串型別的 unordered_set 並應用 bucket_size() 函式來計算每個桶中元素的數量並顯示它們。

#include <iostream>
#include <string>
#include <unordered_set>
using namespace std;

int main () {
   unordered_set<string> uSet = { "red", "green", "blue", "yellow", "purple", "pink" };

   unsigned nbuckets = uSet.bucket_count();

   cout << "uSet has " << nbuckets << " buckets:\n";

   for (unsigned i=0; i<nbuckets; ++i) {
      cout << "bucket #" << i << " has " << uSet.bucket_size(i) << " elements: ";
      for (auto it = uSet.begin(i); it!=uSet.end(i); ++it)
         cout << "[" << *it<< "] ";
      cout << "\n";
   }

   return 0;
}

輸出

上面程式碼的輸出如下：

uSet has 13 buckets:
bucket #0 has 2 elements: [purple] [red] 
bucket #1 has 0 elements: 
bucket #2 has 1 elements: [blue] 
bucket #3 has 1 elements: [green] 
bucket #4 has 0 elements: 
bucket #5 has 0 elements: 
bucket #6 has 1 elements: [yellow] 
bucket #7 has 0 elements: 
bucket #8 has 0 elements: 
bucket #9 has 0 elements: 
bucket #10 has 1 elements: [pink] 
bucket #11 has 0 elements: 
bucket #12 has 0 elements: