unordered_multimap_name.equal_range(k)

// C++ program to illustrate the
// unordered_multimap::equal_range()
#include <iostream>
#include <unordered_map>
using namespace std;
  
int main()
{
  
    // 声明
    unordered_multimap<int, int> sample;
  
    // 插入键和元素
    sample.insert({ 1, 2 });
    sample.insert({ 1, 2 });
    sample.insert({ 2, 3 });
    sample.insert({ 3, 4 });
    sample.insert({ 2, 6 });
  
    // 指向包括1的范围的配对迭代器，并通过在范围内迭代来打印
    auto itr = sample.equal_range(1);
    cout << "Elements with Key 1: ";
    for (auto it = itr.first; it != itr.second; it++) {
        cout << it->second << " ";
    }
  
    cout << endl;
  
    // 指向包括2的范围的配对迭代器，并通过在范围内迭代来打印
    itr = sample.equal_range(2);
    cout << "Elements with Key 2: ";
    for (auto it = itr.first; it != itr.second; it++) {
        cout << it->second << " ";
    }
  
    return 0;
}

Elements with Key 1: 2 2 
Elements with Key 2: 6 3

// C++ program to illustrate the
// unordered_multimap::equal_range()
#include <iostream>
#include <unordered_map>
using namespace std;
  
int main()
{
  
    // 声明
    unordered_multimap<char, char> sample;
  
    // 插入键和元素
    sample.insert({ 'a', 'b' });
    sample.insert({ 'a', 'b' });
    sample.insert({ 'a', 'd' });
    sample.insert({ 'b', 'e' });
    sample.insert({ 'b', 'd' });
  
    // 指向包括b的范围的配对迭代器，并通过在范围内迭代来打印
    auto itr = sample.equal_range('b');
    cout << "Elements with Key b: ";
    for (auto it = itr.first; it != itr.second; it++) {
        cout << it->second << " ";
     }
  
    cout << endl;
  
    // 指向包括a的范围的配对迭代器，并通过在范围内迭代来打印
    itr = sample.equal_range('a');
    cout << "Elements with Key a: ";
    for (auto it = itr.first; it != itr.second; it++) {
        cout << it->second << " ";
    }
  
    return 0;
}

Elements with Key b: d e 
Elements with Key a: d b b