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

unordered_multimap::equal_range()是C++ STL中的內置函數，該函數返回所有元素的鍵都等於鍵的範圍。它返回一對迭代器，其中第一個是指向範圍下限的迭代器，第二個是指向範圍上限的迭代器。如果容器中沒有等於給定值的元素，則它將返回一對上下限都指向容器或unordered_multimap.end()末尾的位置。

用法:

unordered_multimap_name.equal_range(k)

參數：該函數接受強製性參數k。返回的範圍將包含鍵為k的元素。

返回值：它返回一對迭代器。

以下示例程序旨在說明上述函數：

示例1:

// C++ program to illustrate the 
// unordered_multimap::equal_range() 
#include <iostream> 
#include <unordered_map> 
using namespace std; 
  
int main() 
{ 
  
    // declaration 
    unordered_multimap<int, int> sample; 
  
    // inserts key and element 
    sample.insert({ 1, 2 }); 
    sample.insert({ 1, 2 }); 
    sample.insert({ 2, 3 }); 
    sample.insert({ 3, 4 }); 
    sample.insert({ 2, 6 }); 
  
    // iterator of pairs pointing to range 
    // which includes 1 and print by iterating in range 
    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; 
  
    // iterator of pairs pointing to range 
    // which includes 2 and print by iterating in range 
    itr = sample.equal_range(2); 
    cout << "Elements with Key 2: "; 
    for (auto it = itr.first; it != itr.second; it++) { 
        cout << it->second << " "; 
    } 
  
    return 0; 
}

輸出：

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

示例2:

// C++ program to illustrate the 
// unordered_multimap::equal_range() 
#include <iostream> 
#include <unordered_map> 
using namespace std; 
  
int main() 
{ 
  
    // declaration 
    unordered_multimap<char, char> sample; 
  
    // inserts key and element 
    sample.insert({ 'a', 'b' }); 
    sample.insert({ 'a', 'b' }); 
    sample.insert({ 'a', 'd' }); 
    sample.insert({ 'b', 'e' }); 
    sample.insert({ 'b', 'd' }); 
  
    // iterator of pairs pointing to range 
    // which includes b and print by iterating in range 
    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; 
  
    // iterator of pairs pointing to range 
    // which includes a and print by iterating in range 
    itr = sample.equal_range('a'); 
    cout << "Elements with Key a: "; 
    for (auto it = itr.first; it != itr.second; it++) { 
        cout << it->second << " "; 
    } 
  
    return 0; 
}

輸出：

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

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 equal_range() 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。