📜  C++ STL中的unordered_set count()函数

📅  最后修改于: 2021-05-30 16:36:55             🧑  作者: Mango

unordered_set :: count()函数是C++ STL中的内置函数,用于对unordered_set容器中特定元素的出现进行计数。由于unordered_set容器不允许存储重复的元素,因此该函数通常用于检查容器中是否存在元素。如果元素存在于容器中,则该函数返回1,否则返回0。

语法

unordered_set_name.count(element)

参数:此函数接受单个参数元素。此参数表示容器中是否存在需要检查的元素。

返回值:如果元素存在于容器中,则此函数返回1,否则返回0。

下面的程序说明了unordered_set :: count()函数:

程序1

// CPP program to illustrate the
// unordered_set::count() function
  
#include 
#include 
  
using namespace std;
  
int main()
{
  
    unordered_set sampleSet;
  
    // Inserting elements
    sampleSet.insert(5);
    sampleSet.insert(10);
    sampleSet.insert(15);
    sampleSet.insert(20);
    sampleSet.insert(25);
  
    // displaying all elements of sampleSet
    cout << "sampleSet contains: ";
    for (auto itr = sampleSet.begin(); itr != sampleSet.end(); itr++) {
        cout << *itr << " ";
    }
  
    // checking if element 20 is present in the set
    if (sampleSet.count(20) == 1) {
        cout << "\nElement 20 is present in the set";
    }
    else {
        cout << "\nElement 20 is not present in the set";
    }
  
    return 0;
}
输出:
sampleSet contains: 25 5 10 15 20 
Element 20 is present in the set

程序2

// C++ program to illustrate the
// unordered_set::count() function
  
#include 
#include 
  
using namespace std;
  
int main()
{
  
    unordered_set sampleSet;
  
    // Inserting elements
    sampleSet.insert("Welcome");
    sampleSet.insert("To");
    sampleSet.insert("GeeksforGeeks");
    sampleSet.insert("Computer Science Portal");
    sampleSet.insert("For Geeks");
  
    // displaying all elements of sampleSet
    cout << "sampleSet contains: ";
    for (auto itr = sampleSet.begin(); itr != sampleSet.end(); itr++) {
        cout << *itr << " ";
    }
  
    // checking if element GeeksforGeeks is
    // present in the set
    if (sampleSet.count("GeeksforGeeks") == 1) {
        cout << "\nGeeksforGeeks is present in the set";
    }
    else {
        cout << "\nGeeksforGeeks is not present in the set";
    }
  
    return 0;
}
输出:
sampleSet contains: Welcome To GeeksforGeeks For Geeks Computer Science Portal 
GeeksforGeeks is present in the set
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